In many cartoon shows, a character runs off a cliff, realizes his predicament, and lets out a scream. He continues to scream as he falls. If the physical situation is portrayed correctly, from the vantage point of an observer at the top of the cliff leaning over the edge, the pitch of the scream as he falls should be.

A) higher than the original pitch and constant.
B) higher than the original pitch and increasing as he falls.
C) lower than the original pitch and constant.
D) lower than the original pitch and decreasing as he falls.
E) It is impossible to predict.

D) lower than the original pitch and decreasing as he falls.

Explanation:

Let's begin by explaining the following:

The Doppler effect is the change in a wave (sound in this case) perceived frequency when the emitter of the waves, and the receiver move relative to each other.  

To understand it better: It is the variation of the frequency of a wave due to the relative movement of the source of the wave with respect to its receiver.

For example, as the source of the sound moves closer to the receiver, the frequency is increased; but as the source of the sound moves away from the receiver, the frequency is lowered.

Now, the pitch of a sound has a close relation with the frequency, hence if the frequency is lower, the pitch is lower as well.

This means that as the character screams as he falls and moves farther from the receiver locaated at the top of the cliff, his pitch will be lower than the original pitch and decreasing as he falls.

Therefore, the correct option is:

D) lower than the original pitch and decreasing as he falls.