I often go to work ________. [ ] A. ride

---I haven’t seen Jack for three days, is he ill?

---_______. His mother told me that he was in hospital.

A．I am afraid so

B．I hope not

C．I don’t expect

D．I am afraid not

小彬拿20元钱到超市买来果汁x瓶，酸奶y瓶，找回7元，已知果汁每瓶2元，酸奶每瓶3元，列出关于x、y的二元一次方程为______．

蜻蜓点水是蜻蜓在进行一项重要的生命活动，这项活动是______．

Did you know           ?          [ ]

A. whom was Bill waiting for                  

B. whom is Bill waiting for          

C. whom Bill was waiting for                

D. whom Bill is waiting for

内部增长率(internal growth rate)