题目

—Why didn't you try your best to get on the subway? —I tried to, but it started moving_________I could get on it. A. before       B. after       C. since           D. if 答案：A水的比热容是煤油比热容的2倍，那么质量之比为1：4的水和煤油：（1）使这些水和煤油升高相同的温度，它们吸收的热量之比是1：21：2；（2）使这些水和煤油吸收相同热量后，它们升高的温度之比是2：12：1．