What is the number of chromosomes in a secondary spermatocyte?

Total number of primordial follicles which remain in the ovary of human females at the time of puberty are . . . . . . .

Given a diagram showing a portion of a seminiferous tubule. Identify the marked alphabets.

Which organelle is important for spermiogenesis and forms the acrosome?

The membrane investing the ovum just outside the membrana granulosa is

Arrange the following cell layers/structures around the female gamete, from outer to inner side :
$A$. Zona pellucida
$B$. Perivitelline space
$C$. Corona radiata
$D$. Plasma membrane of ovum