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.

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

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

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

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

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

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

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

Ovulation can be detected by

The placenta helps in the maintenance of pregnancy by secreting a hormone, known as

Assertion : Corpus luteum degenerates in the absence of fertilization.

Reason : Progesterone level decreases.

Which one of the following statements is incorrect about menstruation?