Answer & Explanation:
Crest is a point in the cycle where maximum or peak amplitude exists. In another way, it is a point on the positive side of a wave where maximum amplitude exits. Trough is a point in the cycle where minimum amplitude exists.
Crest: points A and E
Trough: points C and J
Wavelength is the distance between two crests or two troughs. One example is distance between points A and E.
Frequency is 3 because there are 3 oscillations in 1 second (follow the line from beginning to point D, then D to G, the G to end).
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