"Hello?"

Consider the following telephone dialogue:

(ring!)
(ring!)
Callee: "Hello?"
Caller: "Hello?"

What is wrong with this dialogue? Choose the right answer:

(a) Nothing.
(b) The caller is not supposed to say hello. That's the callee's job. The caller's job is to identify himself or herself, and state his or her reason for calling.
(c) None of the above.
(d) All of the above.

The right answer is (b).