Which statement is true about the male reproductive system?
a. the testes produce semen.
b. sperm cells are the largest component in the composition of semen.
c. the scrotum functions to keep the testes at an optimum temperature.
d. the penis enables sperm to be deposited directly into the uterus.

C. The scrotum functions to keep the testes at an optimum temperature.

Explanation:

In order to understand the correct answer, we need to review basic anatomy and physiology of male reproductive system.

Testes also known as testicles are paired organs located in the scrotum (bag of skin and smooth muscle) suspended from the body. Testes are responsible for the formation of sperms. Scrotum keeps the testicles away from the body. It provides a temperature cooler than the body temperature which is necessary for formation of sperms (Spermatogenesis). Sperms mix with other secretions from various internal genital organs (prosate, Cowper's glands, seminal vesicles) to form semen. Sperms constitute a very small proportion of semen.

Semen is deposited by the penis into vaginal tract from where the sperms travel to uterus.

Coming back to the answer choices,

A. The testes produce semen.

Testes produce sperms and semen is formed after sperms mix with other secretions of organs of male reproductive system.

B. Sperm cells are the largest component in the composition of semen.

Sperms constitute a small proportion of semen. Other components of semen include fructose, fibrinogen, coagulants, cholesterol etc.

C. The scrotum functions to keep the testes at an optimum temperature.

This is the correct answer choice as scrotum keeps testicles away from the body at a suitable temperature for spermatogenesis.

D. The penis enables sperm to be deposited directly into the uterus.

Penis deposits semen into the vaginal tract from where sperms travel to the uterus.

interphase

the period of cell growth when the cell synthesizes new molecules and organelles. the cell is not dividing and it constitutes the majority of the time spent in the cell cycle

prophase

changes occur in the nucleus and cytoplasm. the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still in tact

prometaphase

the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the sister chromatids

metaphase

all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle

anaphase

begins when sister chromatids separate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell

telophase

the daughter nuclei form at the two poles of a cell

cytokinesis

the division of a cytoplasm to form two separate daughter cells. usually occurs during telophase during mitosis. this and mitosis make up to mitotic (m) phase of the cell cycle