What is the difference between a primary oocyte and a secondary oocyte?

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 :

Which of the following vitamins is essential for gametogenesis?

Select the odd one out.

Who discovered human sperm?

Where is the germ hill (cumulus oophorus) present?