Answer:
(C)
Step-by-step explanation:
The question is saying: "You receive an email from an unknown source."
A means "Read the email and then reply to it"
B means "Contact the person who sent it to you"
C means "Immediately delete the email'
D means "Reply with your contact details"
In this situation, we would not use D since this information should not be put out. You should also not reply to it unless you know who it is. Now it's just B & C. B is just like A, so that leaves us with C.