Excess vitamin a is most harmful to an embryo during the months of pregnancy.

Hey You!

I believe the answer would be:

Excess Vitamin A is most harmful to an embryo during the first and second months of pregnancy.

Please do let me know whether or not this helped you out.

Iam not sure but to me it with be a or dsorry if i was late! hope this ! : )if you really want me to find out the answer that is correct tell me and i will do more research but the a or d makes sense to me.