题目: 1!+2!+3!+…+2010!的个位数是()。A.1B.3C.4D.5 答案: 参考答案:B解析: 1!=1、2!=2、3!=6、4!=24、当n≥5时,n!的尾数为0。则原式各项的尾数之和是1+2+6+4+0=13,故所求的个位数是3。
题型:选择题 The government has taken some measures to solve the shortage of electricity, but it may be some time ________ the situation improves.[ ]A. since B. whenC. unless D. before 查看答案