从A、B、C、D四个选项中，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
21．If you want to study nature of universe, first of all, you must be clear about the origin of it．
A．不填；the B．the；不填 C．the ; the D．不填；不填
22．— Excuse me ,could you show me the way to the railway station?
— ． In fact , I’m a stranger here myself．
A．I think so B．I’m afraid not C．I hope not D．I’d rather not
