Which of the following is the horizontal distance between two successive crests?

Wave length

The correct answer is option 4. Wave length.

The horizontal distance between two successive crests of a wave is called Wave length.

Wave length (often denoted by the symbol λ) is a fundamental property of a wave and represents the distance between two consecutive points on a wave that are in phase, such as two successive crests or troughs. It is commonly measured in meters (m) or other units of length. Wave length is one of the key parameters used to characterize waves and is related to other wave properties such as frequency and speed.