When two waves interact with their crests and troughs in alignment is called?

When two waves interact with their crests and troughs in alignment is called constructive interference. If two waves of the same wavelength occupy the same space in such a way that their crests and troughs align, the wave they produce will have an amplitude greater than that possessed by either wave initially. This is known as constructive interference. The more closely the waves are in phase—that is, perfectly aligned—the more constructive the interference.

Constructive interference.

Explanation:

Constructive interference is the interference which  occurs when the peak of the two waves add together and the condition is that these two waves are in same phase, so that the resulting wave amplitude  is equal to the addition of the individual amplitudes.

Crest is the highest point of the wave. Trough is defined as the lowest amplitude of the wave. The occurrence of constructive interference will occurs  when the peaks of the  two waves meet and overlap which is called the alignment of crest and trough.

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d is the correct answer