Question

part a - required conditions for conception
specific conditions have to be present for a pregnancy to result from vaginal intercourse. conception occurs when a sperm fertilizes an egg, usually in the fallopian tube. if no birth control or contraception is used, 85% of women having sex will become pregnant in 1 year.
choose the answer which best describes that the conditions required for conception have been met.
view available hint(s)
vaginal intercourse occurs 3.5 days after ovulation without the use of any form of birth control.
a couple has unprotected sex 5 days before the egg is present in the fallopian tube.
unprotected sex occurs 9 days before ovulation, and approximately 300 million sperm are ejaculated.
unprotected sex occurs 15 days after ovulation, and 80% of the sperm are destroyed during the journey to the fallopian tube.

Explanation:

Conception occurs when sperm fertilizes an egg, usually in the fallopian tube. Sperm can survive in the female reproductive tract for about 5 days, and the egg is viable for about 1 - 2 days after ovulation. For conception to occur, sperm and egg need to be present in the fallopian tube at the same time. In the first option, having intercourse 3.5 days after ovulation means the egg may no longer be viable. In the second option, having sex 5 days before the egg is in the fallopian tube means sperm may not survive long enough. In the fourth option, 15 days after ovulation is too late as the egg is no longer viable. In the third option, unprotected sex 9 days before ovulation means sperm can wait in the female reproductive tract until ovulation occurs and then fertilize the egg.

Answer:

Unprotected sex occurs 9 days before ovulation, and approximately 300 million sperm are ejaculated