题目

Charlie made a(n) ________ to apologize for what he had done，but his classmates wouldn't even talk to him. A．promise  B．progress C．attempt  D．reputation 答案：C [make an attempt to do sth.“试图做某事”，符合语境。make a promise “做出承诺”； make progress “取得进展”；make a reputation “树立声誉”。]用纯净的碳酸钙与稀盐酸反应制取二氧化碳气体，为了加快化学反应的反应速率，下列措施你认为可行的是A.加入蒸馏水B.加热C.加入NaCl溶液D.加入浓盐酸