What Do We Mean When We Say That Two Light

Multiple Choice

What do we mean when we say that two light rays striking a screen are in phase with each other?

A) They alternately reinforce and cancel each other.
B) They are traveling at the same speed.
C) They have the same wavelength.
D) When the electric field due to one is a maximum, the electric field due to the other is also a maximum, and this relation is maintained as time passes.