Most sperm cells die in the vagina when entering the female's body because Most sperm cells die in the vagina when entering the female's body because

- the female's reproductive tract is protected by digestive enzymes.

- the sperm cannot pass through the mucus.

- macrophages from the female's immune system destroy all nonself cells.

- of the low pH of the vagina.

- the sperm cells have not yet been activated to swim.

of the low pH of the vagina.

Explanation:

The pH of the vagina is maintained at highly acidic levels to prevent the germ buildup. The range of vaginal pH is around 3.8 to 4.5. The very low pH of the vagina creates a hostile environment for sperms and most of the sperms are killed as they enter the vagina due to the acidic pH.

Apart from supplementing the sperms with energy, cervical mucus serves to protect the sperms from the hostile conditions of the vagina. The cervical mucus has an alkaline pH at or near the ovulation to protect sperms from acidic pH of the vagina and to facilitate fertilization.