What is the ploidy of the polar body produced during oogenesis?

Describe the structure of a sperm.

Given below are two statements:
$Statement-I$: At the onset of puberty, the pituitary gland begins secretion of gonadotropin releasing hormone.
$Statement-II$: $GnRH$ initiates the significant increase in the secretion of follicle stimulating hormone $(FSH)$ which induces gametogenesis.
In light of above statements, choose the correct appropriate answer from the options given below.

For normal fertility,what percentage of sperm in a human male ejaculate must have vigorous motility (in $\%$)?

At which stage of life is the oogenesis process initiated?

Identify the hormone that acts on the cells required for the nourishment of sperm and stimulates them.