2026/2027
South Carolina Physical/Chemical
Wastewater Operator Class C Exam
2026/2027 Comprehensive Study Guide and
Practice Question Review Manual
Question 1:
The crown of a tooth is best described as:
A. The portion below the gum line
B. The most terminal portion of the root
C. The portion above the gum line covered by enamel
D. The bone that anchors the tooth
Correct Answer: C. The portion above the gum line covered by enamel
Rationale: The crown is the visible part of the tooth above the gingival margin and is
covered by enamel, the hardest substance in the body. The root lies below the gum
line and anchors the tooth into the alveolar bone. The terminal root portion and
supporting bone are not part of the crown.
Question 2:
What term describes wearing away of enamel due to tooth-to-tooth contact?
A. Abrasion
B. Attrition
C. Erosion
D. Caries
Correct Answer: B. Attrition
Rationale: Attrition is mechanical wear caused by tooth-to-tooth contact during
chewing. Abrasion results from external objects (e.g., toothbrush). Erosion is
chemical dissolution from acids, while caries involve bacterial decay.
Question 3:
A thin film composed of bacteria, saliva, and food debris on teeth is called:
A. Calculus
B. Plaque
,2026/2027
C. Enamel
D. Tartar
Correct Answer: B. Plaque
Rationale: Plaque is a soft biofilm that forms on teeth. If not removed, it hardens into
calculus (tartar). Enamel is the hard outer tooth layer and is not a deposit.
Question 4:
Which imaging method does NOT use ionizing radiation?
A. CT scan
B. X-ray
C. Fluoroscopy
D. Ultrasound
Correct Answer: D. Ultrasound
Rationale: Ultrasound uses sound waves, not ionizing radiation. CT, X-ray, and
fluoroscopy all use ionizing radiation, which carries exposure risk.
Question 5:
What occurs when crystals in an ultrasound transducer receive electrical pulses?
A. They melt
B. They harden
C. They vibrate
D. They dissolve
Correct Answer: C. They vibrate
Rationale: Piezoelectric crystals vibrate when electrically stimulated, producing
ultrasound waves used for imaging.
Question 6:
Ultrasound imaging typically displays how many shades of gray?
A. 128
B. 200
C. 256
D. 512
,2026/2027
Correct Answer: C. 256
Rationale: Ultrasound images are commonly represented in 256 grayscale levels,
allowing detailed tissue differentiation.
Question 7:
The gain control on an ultrasound machine adjusts:
A. Depth of imaging
B. Image brightness
C. Pulse frequency
D. Sound wave speed
Correct Answer: B. Image brightness
Rationale: Gain amplifies returning echoes, increasing overall image brightness
without changing actual signal strength.
Question 8:
Time gain compensation (TGC) allows:
A. Adjustment of depth only
B. Adjustment of gain at different depths
C. Reduction of sound speed
D. Elimination of artifacts
Correct Answer: B. Adjustment of gain at different depths
Rationale: TGC compensates for signal weakening at deeper tissues, allowing
uniform image brightness.
Question 9:
Proper disinfection of an ultrasound probe includes:
A. Autoclaving
B. Alcohol immersion only
C. Glutaraldehyde-based wipe
D. Dry cloth wiping only
Correct Answer: C. Glutaraldehyde-based wipe
, 2026/2027
Rationale: High-level disinfection with chemical agents like glutaraldehyde is
required; autoclaving may damage probes.
Question 10:
A comet-tail artifact occurs when ultrasound interacts with:
A. Bone
B. Fluid
C. Metal or air
D. Soft tissue
Correct Answer: C. Metal or air
Rationale: Strong reflectors like metal or gas cause reverberation artifacts known as
comet tails.
Question 11:
Hypoechoic tissue appears as:
A. Bright white
B. Dark gray
C. Black
D. Radiopaque white
Correct Answer: B. Dark gray
Rationale: Hypoechoic structures reflect fewer echoes and appear darker than
surrounding tissues.
Question 12:
A dorsoventral radiographic view means:
A. Beam enters ventral surface
B. Beam enters dorsal surface
C. Beam enters lateral surface
D. Beam enters cranial surface
Correct Answer: B. Beam enters dorsal surface
Rationale: Dorsoventral means X-ray enters dorsally and exits ventrally.
South Carolina Physical/Chemical
Wastewater Operator Class C Exam
2026/2027 Comprehensive Study Guide and
Practice Question Review Manual
Question 1:
The crown of a tooth is best described as:
A. The portion below the gum line
B. The most terminal portion of the root
C. The portion above the gum line covered by enamel
D. The bone that anchors the tooth
Correct Answer: C. The portion above the gum line covered by enamel
Rationale: The crown is the visible part of the tooth above the gingival margin and is
covered by enamel, the hardest substance in the body. The root lies below the gum
line and anchors the tooth into the alveolar bone. The terminal root portion and
supporting bone are not part of the crown.
Question 2:
What term describes wearing away of enamel due to tooth-to-tooth contact?
A. Abrasion
B. Attrition
C. Erosion
D. Caries
Correct Answer: B. Attrition
Rationale: Attrition is mechanical wear caused by tooth-to-tooth contact during
chewing. Abrasion results from external objects (e.g., toothbrush). Erosion is
chemical dissolution from acids, while caries involve bacterial decay.
Question 3:
A thin film composed of bacteria, saliva, and food debris on teeth is called:
A. Calculus
B. Plaque
,2026/2027
C. Enamel
D. Tartar
Correct Answer: B. Plaque
Rationale: Plaque is a soft biofilm that forms on teeth. If not removed, it hardens into
calculus (tartar). Enamel is the hard outer tooth layer and is not a deposit.
Question 4:
Which imaging method does NOT use ionizing radiation?
A. CT scan
B. X-ray
C. Fluoroscopy
D. Ultrasound
Correct Answer: D. Ultrasound
Rationale: Ultrasound uses sound waves, not ionizing radiation. CT, X-ray, and
fluoroscopy all use ionizing radiation, which carries exposure risk.
Question 5:
What occurs when crystals in an ultrasound transducer receive electrical pulses?
A. They melt
B. They harden
C. They vibrate
D. They dissolve
Correct Answer: C. They vibrate
Rationale: Piezoelectric crystals vibrate when electrically stimulated, producing
ultrasound waves used for imaging.
Question 6:
Ultrasound imaging typically displays how many shades of gray?
A. 128
B. 200
C. 256
D. 512
,2026/2027
Correct Answer: C. 256
Rationale: Ultrasound images are commonly represented in 256 grayscale levels,
allowing detailed tissue differentiation.
Question 7:
The gain control on an ultrasound machine adjusts:
A. Depth of imaging
B. Image brightness
C. Pulse frequency
D. Sound wave speed
Correct Answer: B. Image brightness
Rationale: Gain amplifies returning echoes, increasing overall image brightness
without changing actual signal strength.
Question 8:
Time gain compensation (TGC) allows:
A. Adjustment of depth only
B. Adjustment of gain at different depths
C. Reduction of sound speed
D. Elimination of artifacts
Correct Answer: B. Adjustment of gain at different depths
Rationale: TGC compensates for signal weakening at deeper tissues, allowing
uniform image brightness.
Question 9:
Proper disinfection of an ultrasound probe includes:
A. Autoclaving
B. Alcohol immersion only
C. Glutaraldehyde-based wipe
D. Dry cloth wiping only
Correct Answer: C. Glutaraldehyde-based wipe
, 2026/2027
Rationale: High-level disinfection with chemical agents like glutaraldehyde is
required; autoclaving may damage probes.
Question 10:
A comet-tail artifact occurs when ultrasound interacts with:
A. Bone
B. Fluid
C. Metal or air
D. Soft tissue
Correct Answer: C. Metal or air
Rationale: Strong reflectors like metal or gas cause reverberation artifacts known as
comet tails.
Question 11:
Hypoechoic tissue appears as:
A. Bright white
B. Dark gray
C. Black
D. Radiopaque white
Correct Answer: B. Dark gray
Rationale: Hypoechoic structures reflect fewer echoes and appear darker than
surrounding tissues.
Question 12:
A dorsoventral radiographic view means:
A. Beam enters ventral surface
B. Beam enters dorsal surface
C. Beam enters lateral surface
D. Beam enters cranial surface
Correct Answer: B. Beam enters dorsal surface
Rationale: Dorsoventral means X-ray enters dorsally and exits ventrally.
