1、【解析】C.直接用选项代入。
2、【解析】A.把每一个数的末三位相加即可，也即7+77+777×75=58359.
3、【解析】B.如使结果最小，则划掉两个数字后的算式应为18+99,其值约为0.18181818……，显然为18循环，则第1998位应为8.
4、【解析】D.用户改装新表12个月共花费电费（0.28×100+0.56×100）×12=1008元，改装费100元；改装前所耗电费为0.53×200×12=1272元，所以共节省1272-1008-100=164元。
5、【解析】B.
解法一、看过的人为62+34-11=85,没有看过的自然是15.
解法二、用容斥原理，100=62+34-11+x,尾数为5.
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