根据表格数据可推知所用凸透镜的焦距f满足 [ ] A．6cm＜f＜26cm B．

If you ________ yesterday，you ________ with your mother now.[ ]

A．set off; would talk

B．had set off; would be talking

C．set off; would have talked

D．had set off; would talk

若(1+x)+(1+x)²+…+(1+x)ⁿ=a₁(x-1)+2a₂(x-1)²+…+na_n(x-1)ⁿ，则a₁+2a₂+3a₃+…+na_n=( )．

A．

B．

C．

D．

E．

胃液分析显示胃酸缺乏者，应考虑是（）

A.胃溃疡

B.慢性浅表性胃炎

C.A型胃炎

D.胃息肉

E.胃泌素瘤

从所给的四个选项中，选择最合适的一个填入问号处，使之呈现一定的规律性。（）

A．

B．

C．

D．