Is it work or works?

Question

is it " Dystrophin is part of a protein complex that works together to strengthen muscle fibers and protect them from injury as muscles contract and relax." or " Dystrophin is part of a protein complex that work together to strengthen muscle fibers and protect them from injury as muscles contract and relax.

Answer 1

I would reword the definition of Dystrophin. How about "Dystrophin is part of a protein complex which strengthens muscle fibers, protecting them from injury as muscles contract and relax." or "A protein complex, Dystrophin, strengthens and protects muscle fibers from injury as muscles contract and relax."

Answer 2

The correct answer is the first one. The reason is a question of subject-verb agreement. The subject in this case is complex. It is singular, so the verb needs to be as well. Hence, works is the correct choice.

Answer 3

The answer is "works" because the verb must agree with "a protein complex." Since the singular article "a" is used with "protein complex," it is a singular subject that requires a singular verb "works."