题目

已知数列{an}中,a3=2,a7=1,又数列{}是等差数列,则a11等于(    ) A.0                    B.             C.                D.-1 答案：B 解析:∵{}是等差数列,∴设公差为d. 则=-=4d. ∴d=. ∴+4d=+4×=. 故a11=.The more you listen to English, ＿＿＿you’ll feel in speaking English． A．the well       B．easily  C．the more easily     D．the easier