The correct answer is:
A. If the distance between the crests of the waves increase, the frequency decreases.
Explanation:
Wavelength and frequency are inversely related; this means that as the wavelength (the distance between successive crests) increases, the frequency (the number of crests passing a point per second) decreases. This relationship can be expressed with the formula:
\[ \text{Speed} = \text{Wavelength} \times \text{Frequency} \]
Where:
- Speed is constant in a given medium.
- If wavelength increases, frequency must decrease to keep the product (speed) constant.
Therefore, option A accurately describes the relationship between wavelength and frequency.