Which of the following is not a male sex accessory duct?

The correct answer is Option (2) → Seminal vesicle

The male sex accessory ducts carry the sperms from the testis: rete testis, vasa efferentia, epididymis and vas deferens. The male accessory glands are a separate group that add their secretions to the semen.

Option (1) Rete testis — Incorrect. Rete testis is a duct. The seminiferous tubules open into the vasa efferentia through it.

Option (2) Seminal vesicle — Correct. The seminal vesicles are paired male accessory glands, not ducts. Their secretions form part of the seminal plasma; only the duct of the seminal vesicle joins the vas deferens.

Option (3) Vasa efferentia — Incorrect. Vasa efferentia are ducts that leave the testis and open into the epididymis.

Option (4) Epididymis — Incorrect. The epididymis is a duct located along the posterior surface of each testis; it leads to the vas deferens.

NCERT Extract:
The Male Reproductive System – “… The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens (Figure 2.1b). The seminiferous tubules of the testis open into the vasa efferentia through rete testis. The vasa efferentia leave the testis and open into epididymis located along the posterior surface of each testis. The epididymis leads to vas deferens that ascends to the abdomen and loops over the urinary bladder. It receives a duct from seminal vesicle and opens into urethra as the ejaculatory duct (Figure 2.1a).”
The Male Reproductive System – “… The male accessory glands (Figure 2.1a, b) include paired seminal vesicles, a prostate and paired bulbourethral glands.”