【题目】— What do you think of the present economic situation?
— When big firms reduce their expenses, we ______ know that times are really hard.
A. shall B. could
C. must D. need
在线课程【答案】A
【解析】句意：-----你对目前的经济形势有什么看法？
------当大公司削减他们的开销时，我们就知道这段时期真的很艰难了。这里考查时间状语从句，从句用现在表示将来，主句用将来，故选A。