Acrosome is a part of

The thickness of the vitelline membrane is about:

Given below are two statements :
Statement-$I$ : Each primary oocyte gets surrounded by a layer of granulosa cells and is called a primary follicle.
Statement-$II$ : At puberty,only $60,000-80,000$ primary follicles are left in each ovary.
In the light of the above statements,choose the most appropriate answer from the options given below :

The correct sequence of spermatogenetic stages leading to the formation of sperms in a mature human testis is

How many primary follicles are left in each ovary in a human female at puberty?

The testes of a great majority of mammals are typically enclosed in an extra-abdominal sac,the scrotum. The temperature inside the scrotum is lower than that in the abdomen. What will happen if the temperature of the scrotum is artificially maintained at the level of abdominal temperature?