单项填空
从A、B、C、D四个选项中，选出可以填人空白处的最佳选项．
21．—Why didn’t he come to the meeting?
—The reason this was he forgot．
A．about; why B．for; why C．for; that D．about; that
22．—I think smoking is bad for your health． You see the sign “No Smoking” there．
—Yes, I know． But I simply can’t ．
