###Rationale: The above image represents Orchidometer.
It helps to assess the volume of testicules.
Testicular size > 4cc in volume is the 1st sign of puberty in males.

###Answer: OPTION C IS CORRECT.
###Question: What is the instrument used for?
###Options:
A. Assessment of eye size
B. Stool assessment tool
C. Assess the volume of testicles
D. Growth assessment tool
