用所给词的适当形式填空。 1. The child ________ (stop) running around and read his English in the classroom. 2. The police ________ (be) happy to see that no one was hurt in the accident. 3. The boy ________ (run) away quickly when he heard his father's voice. 4. While the boy ________ (sit) in the library, his teacher came to talk to him. 5. The two young men ________ (see) the aliens when the UFO landed.