Two Beams of Coherent Light Travel Different Paths Arriving at Point

Multiple Choice

Two beams of coherent light travel different paths arriving at point P. If the maximum constructive interference is to occur at point P, what should be the phase difference between the two waves?

A) The phase difference between the two waves is π/4.
B) The phase difference between the two waves is π/2.
C) The phase difference between the two waves is π.
D) The phase difference between the two waves is 2π.
E) The phase difference between the two waves is 5π/2.