Concept:Sperm formation in males needs a temperature slightly lower than the normal body temperature.
Explanation:The scrotal sac lies outside the abdominal cavity.
This position keeps the testes cooler than the rest of the body.
A lower temperature is essential for the production and survival of sperm cells.
If the testes remained inside the abdomen, the higher body heat could destroy sperm or reduce fertility.
Therefore, the descent of the testes into the scrotal sac ensures the required cooler environment.
Answer:D. they require a relatively low temperature