The membrane surrounding the secondary oocyte is called-

The correct answer is Option (4) → Zona pellucida

Option (1) Antrum — Incorrect. The antrum is the fluid-filled cavity of the tertiary follicle, not a membrane.

Option (2) Granulosa layer — Incorrect. Granulosa cells surround the oocyte inside the follicle, but they are a cell layer, not the oocyte’s own membrane.

Option (3) Theca — Incorrect. The theca is the outer wall of the follicle (theca interna and externa).

Option (4) Zona pellucida — Correct. The secondary oocyte forms a new membrane, the zona pellucida, around itself. At fertilisation it blocks the entry of additional sperms.

NCERT Extract:
Gametogenesis – “… The tertiary follicle further changes into the mature follicle or Graafian follicle (Figure 2.7). The secondary oocyte forms a new membrane called zona pellucida surrounding it. The Graafian follicle now ruptures to release the secondary oocyte (ovum) from the ovary by the process called ovulation.”

Figure 2.7 Diagrammatic Section view of ovary