Which word in the following sentence is modified by an adverb?

The soccer player forcefully kicked the ball.

A. Soccer

B. Player

C. Kicked

D. Ball

I would say Kick. How did the player kick the ball. He kicked the ball forcefully

Adverbs typically answer questions like "how" and most commonly end in - ly (but don't be fooled, there's many, many more.)

In this sentence, "forcefully" is telling you HOW the soccer player kicked the ball. A is an adjective, B is a noun, C is a verb, and D is also a noun. Adverbs modify verbs, and since "forcefully" modifies "kicked," the answer is C.