You are composing an e-mail. You want to add a signature to the e-mail. Subsequently, you want to
add another signature to the e-mail. However, you are not able to add multiple signatures.
Which of the following is the most likely cause of the issue?

A.
The e-mail is marked as read.

B.
The e-mail is a reply of a message.

C.
The e-mail is an outgoing message.

D.
Only one signature can be added to the e-mail.