Which of the following animals show the menstrual cycle?
A. Gorillas and Chimpanzees
B. Monkeys and Human
C. Orangutans and monkeys
D. All of these

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Hint:The reproductive cycle in the female primates is called menstrual cycle. The first menstruation begins at puberty and is called menarche.

Complete answer:The menstrual phase is a part of female primates' life. Menstrual flow occurs in this phase and lasts for three to four days. This due to the endometrial lining of the uterus and its blood vessels which form a liquid and flows out through the vagina. Menstruation usually occurs about fourteen days after ovulation, if the released ovum is not fertilized. Lack of menstruation may be indicative of pregnancy. Money, chimpanzees, apes, orangutans, and mammals are primates and they also face the menstrual phase in their life.

So the correct answer is an option (D).

Additional Information:
The estrous cycle consists of cyclic changes in the female reproductive system of non-primate mammals. There is no menstruation at the end of the estrous cycle. The estrogen level in the blood increases. The estrous cycle runs only during the breeding season. The suspension of the estrous cycle is called anestrum. The animals that have only a single estrous cycles run only during the breeding season are called monestrous, for example, fox, deer, bat, and animals that have a recurrence of estrous during the breeding season are called polyestrous for example mouse, squirrel, cow, sheep, pig, horse.

Note: In humans certain environmental factors such as stress, poor health, poor diet, prolonged strenuous exercise, can also affect the menstrual cycle and lead to lack of menstruation. These factors can influence hormone levels i.e. secretion of gonadotropins by the anterior lobe of the pituitary, thus disrupting one or more phases of the cycle.