**Answer:**

The correct answer is D) Elephant.

**Explanation:**

In mammals, the testes are the primary reproductive organs responsible for the production of sperm and the secretion of testosterone. The location of the testes varies among different mammalian species. While most mammals have testes that descend into a scrotum, there are some exceptions, such as the elephant.

**Testes in Dog:**
- In dogs, the testes initially develop inside the abdominal cavity near the kidneys.
- As the dog grows, the testes descend through the inguinal canal into the scrotum.
- The scrotum provides a cooler environment necessary for the proper development and maintenance of sperm.

**Testes in Cow:**
- In cows, the testes also initially develop inside the abdominal cavity.
- However, unlike dogs, the testes do not descend into the scrotum. They remain suspended in the abdominal cavity.
- The absence of a scrotum in cows is due to their evolutionary adaptation to maintain a lower body temperature necessary for sperm production.

**Testes in Bull:**
- Bulls are male cattle, and like cows, their testes also do not descend into the scrotum.
- The testes of a bull remain inside the abdominal cavity, similar to cows.
- This adaptation helps maintain a lower body temperature for optimal sperm production.

**Testes in Elephant:**
- In elephants, the testes do not descend into a scrotum and remain within the abdominal cavity.
- Elephants have a unique reproductive system where the testes are retained inside the body due to their large size and the absence of a scrotum.
- The high body temperature of elephants is not conducive to sperm production, so their testes remain inside the abdomen.

In conclusion, while dogs and some other mammals have testes that descend into a scrotum, animals like cows, bulls, and elephants do not have a scrotum, and their testes remain inside the abdominal cavity.