Questions: By week the embryo is a fetus. a. 12 b. 9 C. 20 d. 4

The answer is the second one (b): 9.

Explanation for each option: a. 12 - By week 12, the embryo has already developed into a fetus. This is too late in the timeline. b. 9 - By week 9, the embryo is considered a fetus. This is the correct answer. c. 20 - By week 20, the fetus is well into the second trimester. This is much later than the transition from embryo to fetus. d. 4 - By week 4, the embryo is still in the very early stages of development and has not yet become a fetus.

Summary: The embryo is considered a fetus by week 9.