Question

find the error with subject-verb agreement. select the incorrect verb and type it correctly. 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 of the verb "increase" is "the apparent frequency" (singular). In subject - verb agreement, a singular subject should take a singular verb. So "increase" (plural - form verb) is incorrect. The correct singular form of the verb for the singular subject "frequency" is "increases".

Answer:

Incorrect verb: increase; Correct verb: increases