NLN Pax Science Exam |Questions and
Answers Latest Updated 2026/2027
(Graded A+)
1. A person blows his breath into a straw that is placed in limewater. The limewater
becomes cloudy because the person's breath contains:
a. Oxygen
b. Nitrogen
c. Carbon dioxide
d. Hydrogen
Correct Answer- c. Carbon dioxide
Rationale: Carbon dioxide reacts with calcium hydroxide (limewater) to form calcium
carbonate, which appears as a milky/cloudy precipitate. This is a classic chemical test for
CO₂ in respiration studies.
2. A person who was in an auto accident has formed a blood clot at the site of the injury.
One event that can lead to formation of a blood clot is that:
a. Red blood cells rupture and release hemoglobin
b. White blood cells secrete antibodies
c. Ruptured platelets release thromboplastin
d. Plasma proteins dissolve fibrin
Correct Answer- c. Ruptured platelets release thromboplastin
Rationale: Platelets release thromboplastin (prothrombin activator), initiating the
clotting cascade that converts fibrinogen into fibrin, forming a stable clot to prevent
blood loss.
3. A student focuses sunlight to a point with a thin converging (convex) lens. Which of
these direct measurements can the student make as a result of this experiment?
, a. Refractive index
b. Wavelength of light
c. Approximate focal length of the lens
d. Speed of light
Correct Answer- c. Approximate focal length of the lens
Rationale: By focusing parallel sunlight rays to a point, the student identifies the focal
point, allowing direct measurement of the focal length, a key optical property of lenses.
4. In ecological succession, the first living thing to colonize a hitherto barren area is called
a:
a. Climax species
b. Pioneer organism
c. Consumer organism
d. Decomposer
Correct Answer- b. Pioneer organism
Rationale: Pioneer species are hardy organisms (e.g., lichens, mosses) that initiate
colonization in barren environments, altering conditions to support more complex life
forms.
5. Unicellular organisms that have a nucleus and can swim with the aid of cilia are
examples of:
a. Bacteria
b. Fungi
c. Protozoans
d. Algae
Correct Answer- c. Protozoans
Rationale: Protozoans are unicellular eukaryotes possessing a nucleus and specialized
structures like cilia for locomotion (e.g., Paramecium).
6. Which of these conditions is associated with smoking?
a. Diabetes
b. Emphysema
c. Arthritis
d. Anemia
Correct Answer- b. Emphysema
, Rationale: Smoking damages alveoli, reducing gas exchange efficiency and leading to
emphysema, a chronic obstructive pulmonary disease (COPD).
7. Which of these quantities is most closely associated with an object's inertia?
a. Velocity
b. Force
c. Mass
d. Acceleration
Correct Answer- c. Mass
Rationale: Inertia is the resistance of an object to changes in motion and is directly
proportional to its mass.
8. Which of these sequences of anatomic organization, from the simplest level to the most
complex, is the correct sequence?
a. Organ → Tissue → Organ system → Organism
b. Tissue → Organ → Organ system → Organism
c. Cell → Tissue → Organism → Organ
d. Organ system → Organ → Tissue → Cell
Correct Answer- b. Tissue → Organ → Organ system → Organism
Rationale: Biological organization progresses from cells → tissues → organs → organ
systems → organism. The option begins at tissue and follows the correct hierarchy
upward.
9. Which part of the cell structure controls the passage of materials into and out of the
cell?
a. Nucleus
b. Cytoplasm
c. Plasma membrane
d. Ribosome
Correct Answer- c. Plasma membrane
Rationale: The plasma membrane is selectively permeable, regulating transport via
diffusion, osmosis, and active transport.
, 10. While working in the chemistry laboratory, a student spills dilute hydrochloric acid on
her hand. What is the first action this student should take?
a. Neutralize with base
b. Dry the hand
c. Flush with large quantities of water
d. Cover with bandage
Correct Answer- c. Flush with large quantities of water
Rationale: Immediate dilution and removal of the acid minimizes tissue damage.
Neutralizing agents are not first-line due to potential heat generation.
11. Within a living cell, oxygen (O₂) moves across the membrane down its concentration
gradient. This process is known as:
a. Osmosis
b. Active transport
c. Diffusion
d. Filtration
Correct Answer- c. Diffusion
Rationale: Diffusion is passive movement of molecules from high to low concentration
without energy expenditure.
12. You cut your finger rather deeply while slicing an apple. Which of these actions should
you take first?
a. Apply pressure
b. Wash with cold running water
c. Apply ointment
d. Bandage immediately
Correct Answer- b. Wash with cold running water
Rationale: Cleaning the wound reduces infection risk by removing debris and pathogens
before further treatment.
13. Students measuring peanut shells and recording differences are studying:
a. Mutation
b. Evolution
c. Variation within a species
d. Adaptation
Answers Latest Updated 2026/2027
(Graded A+)
1. A person blows his breath into a straw that is placed in limewater. The limewater
becomes cloudy because the person's breath contains:
a. Oxygen
b. Nitrogen
c. Carbon dioxide
d. Hydrogen
Correct Answer- c. Carbon dioxide
Rationale: Carbon dioxide reacts with calcium hydroxide (limewater) to form calcium
carbonate, which appears as a milky/cloudy precipitate. This is a classic chemical test for
CO₂ in respiration studies.
2. A person who was in an auto accident has formed a blood clot at the site of the injury.
One event that can lead to formation of a blood clot is that:
a. Red blood cells rupture and release hemoglobin
b. White blood cells secrete antibodies
c. Ruptured platelets release thromboplastin
d. Plasma proteins dissolve fibrin
Correct Answer- c. Ruptured platelets release thromboplastin
Rationale: Platelets release thromboplastin (prothrombin activator), initiating the
clotting cascade that converts fibrinogen into fibrin, forming a stable clot to prevent
blood loss.
3. A student focuses sunlight to a point with a thin converging (convex) lens. Which of
these direct measurements can the student make as a result of this experiment?
, a. Refractive index
b. Wavelength of light
c. Approximate focal length of the lens
d. Speed of light
Correct Answer- c. Approximate focal length of the lens
Rationale: By focusing parallel sunlight rays to a point, the student identifies the focal
point, allowing direct measurement of the focal length, a key optical property of lenses.
4. In ecological succession, the first living thing to colonize a hitherto barren area is called
a:
a. Climax species
b. Pioneer organism
c. Consumer organism
d. Decomposer
Correct Answer- b. Pioneer organism
Rationale: Pioneer species are hardy organisms (e.g., lichens, mosses) that initiate
colonization in barren environments, altering conditions to support more complex life
forms.
5. Unicellular organisms that have a nucleus and can swim with the aid of cilia are
examples of:
a. Bacteria
b. Fungi
c. Protozoans
d. Algae
Correct Answer- c. Protozoans
Rationale: Protozoans are unicellular eukaryotes possessing a nucleus and specialized
structures like cilia for locomotion (e.g., Paramecium).
6. Which of these conditions is associated with smoking?
a. Diabetes
b. Emphysema
c. Arthritis
d. Anemia
Correct Answer- b. Emphysema
, Rationale: Smoking damages alveoli, reducing gas exchange efficiency and leading to
emphysema, a chronic obstructive pulmonary disease (COPD).
7. Which of these quantities is most closely associated with an object's inertia?
a. Velocity
b. Force
c. Mass
d. Acceleration
Correct Answer- c. Mass
Rationale: Inertia is the resistance of an object to changes in motion and is directly
proportional to its mass.
8. Which of these sequences of anatomic organization, from the simplest level to the most
complex, is the correct sequence?
a. Organ → Tissue → Organ system → Organism
b. Tissue → Organ → Organ system → Organism
c. Cell → Tissue → Organism → Organ
d. Organ system → Organ → Tissue → Cell
Correct Answer- b. Tissue → Organ → Organ system → Organism
Rationale: Biological organization progresses from cells → tissues → organs → organ
systems → organism. The option begins at tissue and follows the correct hierarchy
upward.
9. Which part of the cell structure controls the passage of materials into and out of the
cell?
a. Nucleus
b. Cytoplasm
c. Plasma membrane
d. Ribosome
Correct Answer- c. Plasma membrane
Rationale: The plasma membrane is selectively permeable, regulating transport via
diffusion, osmosis, and active transport.
, 10. While working in the chemistry laboratory, a student spills dilute hydrochloric acid on
her hand. What is the first action this student should take?
a. Neutralize with base
b. Dry the hand
c. Flush with large quantities of water
d. Cover with bandage
Correct Answer- c. Flush with large quantities of water
Rationale: Immediate dilution and removal of the acid minimizes tissue damage.
Neutralizing agents are not first-line due to potential heat generation.
11. Within a living cell, oxygen (O₂) moves across the membrane down its concentration
gradient. This process is known as:
a. Osmosis
b. Active transport
c. Diffusion
d. Filtration
Correct Answer- c. Diffusion
Rationale: Diffusion is passive movement of molecules from high to low concentration
without energy expenditure.
12. You cut your finger rather deeply while slicing an apple. Which of these actions should
you take first?
a. Apply pressure
b. Wash with cold running water
c. Apply ointment
d. Bandage immediately
Correct Answer- b. Wash with cold running water
Rationale: Cleaning the wound reduces infection risk by removing debris and pathogens
before further treatment.
13. Students measuring peanut shells and recording differences are studying:
a. Mutation
b. Evolution
c. Variation within a species
d. Adaptation
