What physical properties of sperm make them particularly well-suited for their job?

Normal semen is gray-white in color, translucent and has a musty odor. Its normal volume ranges between 2 to 5 mL. Sperm should possess forward, progressive motility so that when it is presented in the cervix, it can propel itself properly through the cervical mucosa to the uterus, fallopian tubes, and ovum. Semen viscosity is also noted as to forming thin threads when droplet testing are done. Semen pH is alkaline ranging from 7.2 to 8.0.

As to the morphology, the normal sperm has an oval-shaped head approximately 5µm long and 3µm wide and a long flagellar tail approximately 45µm long. It has an acrosomal cap which is critical to ovum penetration that is approximately half of head and covers approximately two thirds of the sperm nucleus. Sperm concentration normal value is  greater than 20 million sperm per milliliter. 

A. radioactive dating

The correct answer is c.