sked to explain _____ he did to make hisstudents so fascinated with his lessons, the teacher paused and thought deeply.

The rivers will become dirtier and dirtier ______ wetake action to protect them.

In no case ________ you are aChinese." Dad told me before 1 went to Japan,

I met my best friend _____ in Leheledu on Halloween night.

Since here it’s too hot for you，you may ________ go to work in a seaside city.