一种电子计算机每秒可做108次运算，它工作5×102秒可做多少次运算？（结果用科学记数法表示）
解：。
— I tried many times, but I still failed to complete the experiment.
— Cheer up. _______ and the problem will be solved. [ ]
A. If have a little effort
B. Having a little effort
C. If you have a bit effort
D. A bit more effort
卫生局对提交申请材料不符合要求的申请人，应当当场或者在规定的时限告知其需要补交内容，这个规定的时限是
A．2个工作日B．2日C．5日D．30日E．3个月
。
。