What is the result of a decrease in the level of progesterone?

In human females,the menstrual cycle can be inhibited by the administration of:

Which cellular layer is shed and undergoes regeneration during the menstrual cycle?

The sequence of hormones during the menstrual cycle is:

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.
$\boxed{\text{Primary follicles}}$
$\downarrow \leftarrow \boxed{A}$
$\boxed{\text{Graafian follicle}}$
$\downarrow \leftarrow \boxed{B}$
$\boxed{\text{Ovum}}$
$\downarrow \leftarrow \boxed{C}$
$\boxed{\text{Corpus luteum}}$

The phase of the menstrual cycle in humans that lasts for $7-8$ days is