1. 我们应该排队等候上公共汽车。
    We should _________ to get on the bus.
2. 昨天Carla因交通事故没能上学。
    The traffic accident stopped Carla _________ to school yesterday.
3. 学生在校时间必须穿校服。
    Students _________ wear school uniforms _________ school days.
4. 等雨停了再走。 
    I won't leave _________ the rain _________.
5. 你听说我们班考完试将去北海公园玩的消息了吗？
    Have you _________ that our class _________ to Beihai Park for an outing after the exam?