Two Sources Are Said to Be Coherent If

Multiple Choice

Two sources are said to be coherent if

A) they are of the same frequency and has a phase of zero.
B) they are of the same frequency and maintain a constant non-zero phase.
C) they are of the same intensity but different frequency and has a phase of zero.
D) they are of the same intensity but different frequency and maintain a constant non-zero phase.
E) (A) and (B)