1、题目52:在等比数列{an}中,已知a1·a6=21,则a2·a5=( )

A. 　may

B. 　must

C. 　will

D. 　can

A. 　open

B. 　to open

C. 　opened

D. 　opening

A. 　may

B. 　can＇t

C. 　must

D. 　needn＇t

A. -1

B. 0

C. 1

D. 　不存在

A. 　Luckily

B. 　Suddenly

C. 　Politely

D. 　Recently

A. 　is

B. 　are

C. 　were

D. 　/

A. 　Don＇t

B. 　Doesn＇t

C. 　Aren＇t

D. 　Can＇t

A. 　make

B. 　made

C. 　makes

D. 　making

A. 　2π

B. 　π

C. 　π/2

D. 　π/4

A. 　deal with

B. 　keep up with

C. 　agree with

D. 　come up with