The answer is C.
The reasoning behind this is because male condoms are only used once and then it's garbage, so cross out D.
Male condoms do not prevent sperm formation, for which sperm formation is performed inside the male's testies, so cross out A.
You can buy male condoms in many places, and none of them need prescriptions, so cross out B.
Condoms are used to protect the female from becoming pregnant by trapping the sperm cells inside the condom, so C is the correct answer. For diaphragms, I do not know a whole lot about them, but since we're already this far, C is the correct answer.