1. Cultural festivals have occurred in every country in the world.

2. When an ogre roared with anger, the prince was hitting its eye with his sword.

3.  While Tam was sorting out the rice flock, sparrows came to help.

4. Frog turned into a handsome prince and married the princess.

5. One day, knights were patrolling around the castle when they heard someone crying for help.

6. Yesterday when he carried a suitcase he was dropping it on his foot.

7. He was breaking his leg when he skied last month.

8. He was sitting down on a chair when I painted it.

9. Lan was sitting in the garden when a wasp stung her on the nose.

10. As we were driving down the hill, a strange object appeared in the sky.

giải thích:

* Công thức mệnh đề chỉ nguyên nhân:

Because/ As/ Since + mệnh đề chỉ nguyên nhân, mệnh đề chỉ kết quả

Ví dụ: (ở câu 10)

*  When + simple past, + past continuous : Khi một hành động đang diễn ra thì một hành động khác xảy đến.

* While + past continuous, simple past

.....

1. Cultural festivals have occurred in every country in the world.

2. When an ogre roared with anger, the prince was hitting its eye with his sword.

3.  While Tam was sorting out the rice flock, sparrows came to help.

4. Frog turned into a handsome prince and married the princess.

5. One day, knights were patrolling around the castle when they heard someone crying for help.

6. Yesterday when he carried a suitcase he was dropping it on his foot.

7. He was breaking his leg when he skied last month.

8. He was sitting down on a chair when I painted it.

9. Lan was sitting in the garden when a wasp stung her on the nose.

10. As we were driving down the hill, a strange object appeared in the sky.

Bạn áp dụng công thức nha : 

Wh+ simple past, + past continuous