Question

look at the text below. if there is an error with subject - verb agreement, select the incorrect verb and type it correctly. otherwise, submit the text without making any changes. the doppler effect results from the fact that as a moving object approaches an observer, the apparent frequency of its sound waves increase.

Explanation:

The subject "the apparent frequency" is singular. In English grammar, a singular subject requires a singular verb. The verb "increase" is plural, so it should be changed to "increases" to maintain subject - verb agreement.

Answer:

The Doppler effect results from the fact that as a moving object approaches an observer, the apparent frequency of its sound waves increases.