During menstruation,the level of progesterone in the blood is:

The diagram below shows various events during the menstrual cycle. Identify the hormones $P, Q, R,$ and $S$.

What happens if the ovum fails to get fertilized?

The reproductive cycle in female primates,such as monkeys,apes,and human beings,is called:

The first menstruation is called $........$,and in humans,the menstrual cycle ceases around the age of $50$ years,which is termed as $........$.

In a $28$ day human menstrual cycle,ovulation occurs on