Answer:
C. ¡Buen día!
Explanation:
Since it is a matter of responding to a "formal" email, <u>idioms</u> or <u>barbarities</u> should not be used. Option B could be, but I would use it more on cards.
<h3><em><u>MissSpanish</u></em></h3>
1. Estoy
2. Éstan
3. La maestra está enferma
4. Está en México
5. Eres
Those are the answers, hope I helped out!