Chia động từ ở thì quá khứ tiếp diễn 

1. I_______________ down the street when it begin to rain ( go )

2. At this time last year, I _______________ an English course ( attend ) 

3 Jim _________________ under the tree when he heard an explosion ( stand

4. The boy  fell and hert himself while he ______________________  a bicyle ( ride )