Tommy : The telephone always rings when I am in the shower and can't hear it
Juanita : But you must be able to hear it; otherwise you couldn't know that it was ringing

Juanita's response shows that she presupposes that:

A. The telephone does not ring when Tommy is in the shower
B. Tommy's callers never telephone except when he is in the shower
C. Tommy's callers sometimes hang up thinking he is not at home
D. Tommy cannot tell that the phone has rung unless he has heard it
E. The telephone does not always function properly