The correct option is
C Follicles of ovary
Oogenesis is the process which takes place in the female reproductive system for the production of egg cells or ova. This process generally takes place in the outer layers of the ovarian follicle. This structure, found in the ovary, basically is a fluid-filled sac and contains an immature egg or oocyte which eventually forms a mature ovum and ruptures the follicle to release itself.
So, the correct answer is 'Follicles of ovary'