Question 21: Mark the letter A, B, C, or D on your answer sheet to indicate the undelined part that needs correction in each of the following questions: Sam found it hard to concentrate on his work because the noise.
Knowledge: Reason clauses
Because + S + V = Because of + N: do, because “the noise” is a noun.
Edit: because => because of
Sam finds it hard to concentrate on work because of the noise.