What Should You Do When You Cannot Respond to a Request

Multiple Choice

What should you do when you cannot respond to a request made in an email?

A) Log off the system and let others presume that you are not online.
B) Set up an automated response to say that you are out of town.
C) Inform the sender that you are busy and cannot reply straightaway.
D) Reply immediately and explain how soon you can respond in full.
E) Ignore the email for now and reply when you can.