I think that the answer is coins.
D is the correct answer.
In the badly drawn diagram attached, you will find the <em>yellow</em> represents wavelength, which is the distance between identical points on consecutive waves.
The <em>green</em> represents the amplitude, which is the distance between the origin (middle) and crest/trough (top/bottom)
Answer and explanation:
The musician can play different notes by pulling more or less on the washbasin mast due to the tension applied on the string.
This is because the more the mast is pulled, the more the washtub bass string is stretched and this increases the tension on that string. The stresses determine the type of note that will be exposed. This is because the higher the desired note, the more tension must be applied to the string, so the mast must be pulled harder.
