1. The boy who is playing the piano is Ben.

—> The boy playine the piano is Ben.

2. Do you know the man who is coming towards us?

—> Do you know the man coming towards us?

3. The people who are waiting for the bus in the rain are setting wet.

—> The people waiting for the bus in the rain are getting wet.

4. The scientists who researches the causes of cancer are making progress.

 —> The scientists researching the causes of cancer are making progress.

5. The fence which surrounds our house is made of wood.

—> The fence surrounding our house is made of wood. 
6. We have an apartment which overlooks the park.

—> We have an apartment over looks the park.