题目

We can relax ourselves by taking part in school activities after long hours’ study; _______, we can learn a great deal from other students.    A. therefore        B. but        C. however      D. besides 答案：D— Are you willing to live on Mars(火星)?— ___________ It sounds exciting, but it still worries me.A. Of course I am. B. I’m not sure.C. Why not? D. Are you joking?