在1和128之间插入6个数,使它们和这两数成等比数列,则这6个数的和为( )A.126 B.127 C.257 D.255 答案:解析:设a1=1,a8=128,∴128=1·q7,q=2.插入的6个数中首项为2,公比为2,∴S6==126.答案:A
完成对话
从A-E中选出可以填入空白处的最佳选项,并将其字母序号填入题前的括号内.选项中有两项为多余选项.
A:Hi, Nancy.(1)________
B:I live in Huanggu District.
A:(2)________
B:I live five miles from school.
A:(3)________
B:By bike, sometimes on foot.
A:(4)________
B:About ten minutes.
A:(5)________
B:No, I don't.It takes too much time.