Primary oocyte covered by a layer of granulosa cell is called .

The correct option is B primary follicle
Oogonia is the female gamete mother cell present in the fetal ovary. Oogonia enters prophase-I of the meiosis-I and gets arrested at this stage. They are now called primary oocyte.
A layer of granulosa cells is laid on the primary oocyte and it is now called primary follicles.
Primary folicles get surrounded by more layers of granulosa cells and a new theca to form a secondary follicle.
After birth, the secondary follicles develops a fluid filled cavity called antrum, and becomes tertiary follicle.
After puberty, the tertiary follicle matures into Graafian follicle.