Final answer:
The correct answer to the question is E) both A and B because the contraction of the cremaster muscles pulls the testes closer to the body and also tenses the scrotal sac for optimal sperm production.
Step-by-step explanation:
The contraction of the cremaster muscles serves several functions related to the thermoregulation of the testes and sperm production.
One of these functions is to pull the testes closer to the body cavity, where they can absorb body heat and maintain an optimal temperature for sperm production.
Additionally, the contraction contributes to the wrinkling or tensing of the scrotal sac to reduce its surface area, also aiding in temperature regulation. Therefore, the correct answer to the student's question is E) both A and B, as the cremaster muscles indeed pull the testes closer to the body cavity and tense the scrotal sac.