<p>"The social sciences are fast becoming the most popular majors for undergraduate students at top universities in Europe."</p>
<p>My question is about the phrase "fast becoming". Shouldn't it be "quickly becoming"? I know that "run fast" should be "run quickly" and I don't see how this sentence is any different. The answer key lists it as no error though.</p>
<p>"run fast" is fine because fast is both an adjective and adverb. "quick" has both forms so "run quick" is wrong and should be "run quickly."</p>
<p>take it from an English teacher!</p>
<p>Okay I think I understand it now. So "fast car" - "run fast" and "quick car" - "run quickly"?</p>
<p>Yes, although "run quick" is less common than "run fast". Word combinations are sometimes more habitual than grammatical.</p>
<p>You will also hear " run quick" on analogy with "be quick". In "be quick" quick is a predicate adjective --not adverb.</p>