In addition to sperm, semen: a. contains fluid produced by the secondary bladder
b. contains ejaculum, the fluid released into the ejactulatory duct from the pair of seminal vesicles
c. is made up of fluid from the Cowper's gland
d. contains secretions from three different accessory glands

d. contains secretions from three different accessory glands

Explanation:

The semen is not only made up of sperm. It also consists of secretions coming from three accessory glands: seminal vesicles, prostate gland and bulbourethral gland.

The seminal vesicles secrete proteins, citric acid, sugar, etc. and this accounts for 2/3 volume of the semen. It has a white color that has a tinge of brown.

The prostate glad, on the other hand, secretes a fluid that accounts for 1/3 volume of the semen. This contains the Prostate Specific Antigen (PSA) that thins the semen.

The bulbourethral gland is also known as "Cowper's gland." This produces a secretion that ensures the sperm's motility.