Constructive Interference of Two Coherent Waves Will Occur If the Path

Multiple Choice

Constructive interference of two coherent waves will occur if the path difference is

A) 1/4 $\lambda$ .
B) 6/4 $\lambda$ .
C) 6/2 $\lambda$ .
D) 3/4 $\lambda$ .
E) 3/2 $\lambda$ .