Formation of a secondary oocyte occurs during formation of a secondary oocyte occurs during the luteal phase pregnancy the follicular phase ovulation

The answer is follicular phase. The phase is dominated by the estradiol hormone and Follicle Stimulating Hormone (FSH). Estradiol is mainly produced within the follicles of the ovaries and is responsible for female characteristics. FSH promotes folliculogenesis, a process  in the formation of the secondary oocyte. Follicular phase precedes leutal phase that begins from ovulation