To determine which of the graph of waves represents the high pitch sound we must have into account the concept of frequency.
Frequency is the number of cycles a wave completes per unit of time. The frequency in a graph determines how close together the crests of the wave are. For example:
In the image, one cycle is complete in 2pi/17. But in the next wave:
One cycle is completed in 5pi/8. Therefore, the second example has a higher frequency. We notice that in the second wave the crests are closer than in the first.
A high pitch is associated with a higher frequency. Therefore, the wave for the higher pitch must be the one with the higher frequency. The wave with the higher frequency is the one where the crests are closer together. Therefore, the higher pitch is represented in wave B.