What never ask questions but is always answered, what am I?

Question

Consider that,

A – always says Truth
B – always lies
C – sometimes lies
D – deaf and dumb

What is maximum questions you need to ask each to determine who is ABCD?

Answer 1

a doorbell

Comments

I thought about that one too. But you don't answer the doorbell, you answer the door.

Answer 2

The telephone

Answer 3

Answer:
mobile or door bell

Answer 4

Telephone never ask questions but is always answered