题目

How is it ______ he has made such rapid progress?    A. that        B. why             C. when            D. the on 答案：A  液体的沸点跟液面上的气压有关. 压强增大, 沸点___________________; 压强减小, 沸点____________ A. 升高　　B. 降低　　C. 不变　　D. 先升高后降低