Question

An observer notes that the pitch of a sound is becoming progressively higher. The observer can conclude that the sound is moving

away and the frequency of the sound wave is increasing.
away and the frequency of the sound wave is decreasing.
closer and the frequency of the sound wave is decreasing.
closer and the frequency of the sound wave is increasing.

Answer 1

its the last one D

Step-by-step explanation:

Answer 2

Closer and the frequency of the sound is increasing.

Step-by-step explanation:

This is known as the doppler effect, and is commonly associated with emergency vehicles which move at high speeds with sirens on. While they're not audible from very far away, when they approach the pitch and frequency increase, fading away in opposite fashion as the source moves away.