6. Adults ought to teach children not to throw litter in the streets

⇒Children ought to be taught not to throw litter in the streets.

7.Did they pay him very well for his efforts?

⇒Was he paid very well for his efforts( by them)?

8. He was carrying out a research on how people spend their money for clothes.

⇒A research on how people spend their money for clothes was being researched ( by him)

9.Nowadays, people use English in many fields of the life.

⇒Nowadays, English is used in many fields of the life.

6. Adults ought to teach children not to throw litter in the streets.

-> Children are ought to be taught by adults not to throw litter in the streets.

8. Did they pay him very well for his efforts?

-> Was he paid well by them for his efforts?

9. He was carrying out a research on how people spend their money on clothes.

-> A research on how people spend their money on clothes was being carried out by him.

10. Nowadays, people use English in many fields of the life.

-> 10. Nowadays, English is used in many fields of the life.