1.Bady pandas will be in danger if they ____(leave)alone in the wild.
2.I heard the girl_____(sing)an English song when I passed her window.
3.He got to the station in time ___(catch)the train.
4.The girl stayed there _________(see)ehat would happen to her brother.
5.He has many friends and classmates___(ask)for advice on how learn English well.