Select the sentence that uses the semicolon correctly to separate independent clauses. a. the university student center opened for only two hours, clearly; there must have been some emergency. b. the university student center opened for only two hours. clearly; there must have been some emergency. c. the university student center; opened for only two hours. clearly, there must have been some emergency. d. the university student center opened for only two hours; clearly, there must have been some emergency