In which part of the sperm are mitochondria most abundant?

Spermiogenesis is possible due to....

In oogenesis,when is the secondary oocyte formed in females?

In human females,at the time of birth,there are approximately $2$ million primary oocytes. How many of them normally reach maturity during the entire reproductive life of a female?

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 :

After ovulation,the ruptured Graafian follicle transforms into which structure?