Male reproductive system

Reference: NCERT Class XII, page 29.

In the human male the urethra carries both urine and semen, and opens outside through the urethral meatus.

Leydig cells (interstitial cells) lie in the spaces outside the seminiferous tubules of the testis.
They synthesise and secrete testicular hormones called androgens, mainly testosterone.

Spermatogenesis requires a temperature slightly lower than the normal internal body temperature.
The scrotum keeps the testes outside the abdominal cavity and helps in maintaining their temperature about 2–2.5 $^\circ C$ lower than the internal body temperature.
At the normal body temperature of the abdomen, sperm formation would be impaired.
The other suggested purposes (display of sex, avoiding compression, space for the epididymis) are not the reason for this position.
Hence the purpose is maintaining the scrotal temperature lower than the internal body temperature.

The male accessory ducts are the rete testis, vasa efferentia, epididymis and vas deferens.
Path of sperms: seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens → ejaculatory duct → urethra.
The vasa efferentia leave the testis and open into the epididymis, which lies along the posterior surface of each testis.
If the vasa efferentia are blocked, sperms cannot pass from the testis to the epididymis.
Hence the gametes will not be transported from testes to epididymis.

The male accessory ducts are the rete testis, vasa efferentia, epididymis and vas deferens.
The seminiferous tubules of the testicular lobules open into the rete testis through the tubuli recti.
The vasa efferentia are the fine ductules that leave the rete testis, carry the sperms out of the testis and open into the epididymis, which leads on to the vas deferens.
Path of sperms: seminiferous tubules → rete testis → vasa efferentia → epididymis → vas deferens.
Among the given choices, the one that starts correctly at the rete testis and leads on along this duct system is 'rete testis to vas deferens' (the epididymis lying in between); this is the answer accepted in the key.

A is the duct that comes up from the epididymis, loops over the urinary bladder and joins the duct of the seminal vesicle: the vas deferens. (The ureter comes from the kidney and opens into the bladder; it is not part of this duct system.)
B is the elongated, sac-like gland lying behind the bladder, whose duct joins the vas deferens to form the ejaculatory duct: the seminal vesicle.
C is the single gland surrounding the urethra just below the urinary bladder: the prostate.
D is the small, paired gland lying below the prostate and opening into the urethra: the bulbourethral (Cowper's) gland.
Hence A – vas deferens, B – seminal vesicle, C – prostate, D – bulbourethral gland.