What is the adverb and what does it modify in this sentence: A large portion of the Amazon rain forest grows there.

The adverb is "there." It tells where and modifies the verb, "grows."

The adverb in the sentence is "there." An adverb is a word that modifies or describes a verb, an adjective, or another adverb. In this case, the adverb "there" modifies the verb "grows" by indicating the location where the action is taking place. It tells us that the Amazon rainforest grows in that specific location. To identify the adverb, you can ask yourself the question "Where does the rainforest grow?" and the answer "there" gives you the adverb.