Which word provides the best context clue to the meaning of churning

Coming to school each day, having the necessary materials, and to do homework students to be successful in school. choose the answer that is the most effective substitute for the underlined part of the sentence. if no substitute is necessary, choose ‘leave as is.’ a) leave as is. b) coming to school each day, have the necessary materials, and do homework c) come to school each day, having the necessary materials, and to do homework d) coming to school each day, having the necessary materials, and doing homework