In the following four statements are regarding well defined observable interference pattern.

A. Condition for sustained interference: The two waves should be coherent.

B. Condition for good observation: The separation between light sources should be as small as possible.

C. Condition for good contrast: The amplitudes of interfering waves should be equal (or) at least very nearly equal.

D. Condition for good contrast: Slit width must be very narrow considerably less than the fringe width.