Based on the Information Presented in This Visual, Why Is

Based on the information presented in this visual, why is a folate deficiency most critical during the embryonic period?

A) A folate deficiency is most critical during this period because vitamin B₁₂ tends to be low during this time.
B) A folate deficiency is most critical during this period because iron stores in the mother have been depleted.
C) A folate deficiency is most critical due to the rapid cell division occurring during this period.
D) None of these are correct reasons.