An Employee You Supervise Copies You on a Message to Her

An employee you supervise copies you on a message to her multi-department committee, urging it to finally green light a project. You respond that she has your full support, but you also note that the sole committee member who dissents is obviously wrong and give reasons why. That committee member supervises another department. Later, you receive his terse e-mail stating you should be professional and talk directly to him about your concerns since he is a peer. What MOST likely happened?

A) Your employee blind-copied him on the e-mail, so he received your reply, too.
B) Your employee printed out the e-mail but didn't retrieve it from the shared printer before someone else saw it.
C) You may have hinted at your attitude toward the other supervisor in a department head meeting.
D) The other supervisor is fishing to see what you are saying behind his back.
E) You hit accidentally "reply all" to the message.