Which of the following is seen in the ovulatory phase?
Let's analyse each option - In the ovulatory phase.
Option a: Stimulation of continuation of reduction division of oocytes - correct

During oogenesis, the primary oocyte is arrested in prophase of meiosis


Just before ovulation, the LH surge initiates the continuation of meiosis, forming secondary oocyte and 1st polar body.

"Die LH surge initiates the resumption of meiosis in the oocyte (meiosis is not completed until after the sperm has entered and second polar body is released."
— Leon speroff 8th/ed p 229
Option b: Inhibin A is increased in ovulatory phase - incorrect

Levels of inhibin A are increased and reach a peak in the midluteal phase, not in the ovulatory phase.

Option c: FSH increases steroid synthesis in granulosa cells — incorrect

FSH acts on the granulosa cells to produce estrogen mainly in the follicular phase and not in the ovulatory phase.

Option d: Activin causes FSH to act on the granulose cells — incorrect

As discussed, activin does augment the action of FSH on granulosa cells but during the early follicular phase and not during the ovulatory phase.
"In the granulosa of the early follicular phase, activin augments FSH activities: FSH receptor expression, aromatization, inhibin/ activin production, and LH receptor expression. In the theca, activin suppresses androgen production, allowing the emergence of an estrogen microenvironment."

— Leon speroff 8th/ed p 226.
Stimulation of continuation of reduction division of oocytes
Inhibin A is increased
FSH increases steroid synthesis in granulosa cells
Activin causes FSH to act on granulosa cells