In order to help the student expand his/her knowledge I will help answer the question. This in hope that the student will get a piece of knowledge that will help him/her through his/her homework or future tests.
To have the most impact when using e-mail, you should structure your messages so that the most important information comes first. This was quite simple because if you use common sense out of all the other choices the letter a fits the best and is true.
A. The most important information comes first.
I hope it helps, Regards.