Answer: Bulbourethral glands.
- A Rete testis
- B Epididymis only
- C Seminiferous tubules
- D Bulbourethral glands
Correct answer: D. Bulbourethral glands
Explanation: Secretions of the seminal vesicles, prostate and bulbourethral (Cowper's) glands together make up the seminal plasma of semen.

The human male reproductive system: sperm formed in the testis mature in the epididymis and travel via the vas deferens, mixing with secretions of the seminal vesicle, prostate and bulbourethral glands. Image: Wumingbai, CC BY-SA 4.0, via Wikimedia Commons.
Concept context
Male and female reproductive systems, gametogenesis, fertilization, implantation, pregnancy, and reproductive health.