Regarding causes of infertility, it is the case that

A irregular or failed ovulation is the most common cause of female infertility
B infertility lies in fertility problems of the male partner in about 12% of cases.
C endometriosis result from repeated failure to ovulate
D sperm motility is directly correlated to sperm count

I belive the correct answer is A

2 answers

I believe you're right.
Blocked fallopian tubes — generally resulting from PID (Pelvic Inflammatory Disease) — is the leading cause of female infertility. This is a problem with fallopian tubes rather than ovulation.

Although they may have changed, my statistics for male infertility problems is 18% rather than 12%.

Frankly, I can't see a correct answer for this question as you have stated it.

Sorry that I can't be more helpful. Thanks for asking.