To prevent neural tube birth defects, a woman should take 400 micrograms of folic acid dailya. during the first trimester.b. during the second trimester.c. throughout her childbearing years, if she's capable of conceiving.d. during the last trimester.

Step by Step Solution: Step 1. The woman should take 400 micrograms of folic acid daily. Step 2. Option a. during the first trimester is correct, as this is the time when the neural tube is developing in the fetus. Step 3. Option b. during the second trimester is too late to prevent neural tube defects, and options c. and d. are also incorrect because they do not address the critical time period when the neural tube is developing. Step 4. Therefore, the answer is a. during the first trimester. Final Answer: a. during the first trimester