Before submitting the book reports, proofreading must be done.

A、Thissentencecontainsasquintingmodifier.;
B、Thissentencecontainsbothamisplacedmodifierandadanglingmodifier.;
C、Thissentenceiscorrect.;
D、Thesentenceshouldbecorrectedas“Beforeyousubmitthebookreport,proofreadingmustbedone.”