题目

You should always speak English,______ it’s only ten minutes every day.   A. even if         B. as if                 C. unless        D. because 答案：A 从地面竖直向上抛出一小球，它在2 s内先后两次经过距地面高度为14.7 m的P点，不计空气阻力，该球上抛的初速度为________m/s．