Which one of the following is the most likely root cause why menstruation is not taking place in regularly cycling human female?

About which day in a normal human menstrual cycle does rapid secretion of $LH$ (popularly called $LH$ surge) normally occurs?

Given below is a flow chart showing ovarian changes during menstrual cycle. Fill in the spaces giving the name of the hormones responsible for the events shown.

$\boxed{\rm {Primary follicles}}$

$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \downarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \leftarrow \,\boxed A$

$\boxed{\rm {Graafian follicle}}$

$\,\,\,\,\,\,\,\,\,\,\,\,\,\, \downarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \leftarrow \,\boxed B$

$\,\,\,\,\,\,\,\,\,\,\,\boxed{\rm {Ovum}}$

$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \downarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \leftarrow \,\boxed C$

$\boxed{\rm {Corpus leuteum}}$

Lack of menstruation is caused due to

$A$ : Corpus luteum begins to atrophy after a short life of $10 \;to \;14$ days, if fertilisation does not occur.
$R$ : Luteolysis may be due to withdrawal of $LH$ support

What is menstrual cycle? Which hormones regulate menstrual cycle?