If a female experiences menstruation $6$ times in $12$ months under normal conditions,which of the following can be inferred?

Which types of hormones regulate the menstrual cycle in humans?

The following graph shows the relative concentrations of the four hormones present in the blood plasma of a woman during her menstrual cycle. Identify the hormones $A, B, C$ and $D$.

Given below is a flow chart showing ovarian changes during the menstrual cycle. Fill in the spaces by providing the names of the hormones responsible for the events shown.
$\boxed{\text{Primary follicles}}$
$\downarrow \leftarrow \boxed{A}$
$\boxed{\text{Graafian follicle}}$
$\downarrow \leftarrow \boxed{B}$
$\boxed{\text{Ovum}}$
$\downarrow \leftarrow \boxed{C}$
$\boxed{\text{Corpus luteum}}$

What is the fertile period?

What happens at the beginning of the menstrual cycle?