He runs ___ fast.

1. Very
2. Much
3. More
4. Many

The correct answer is “very” because it is an adverb of degree used to intensify the meaning of another adverb or an adjective. In this case, “fast” is an adverb describing the verb “runs.” To intensify the degree of speed, we use “very.” “Very fast” means to a high degree of speed. The other options are incorrect in this context: “much” is used with comparative adjectives (e.g., much faster) or with uncountable nouns; “more” is the comparative form used for comparisons (e.g., more quickly); and “many” is used with countable nouns. Therefore, “very” is the standard and grammatically correct intensifier for the positive adverb “fast” in this simple declarative sentence.