问题
选择题
—Tom says he is too tired to go on.
—He can’t be.He ____for an hour.
A．just worked
B．has only been working
C．has just worked
D．had only been working
答案
B
考查动词的时态。从本题的语境中可以看出他不可能累的原因是：他从开始工作到现在仅仅才工作了一个小时，因此应该用现在完成进行时。