Could you help me work out the maths problem, Mrs Zhao — . What is it

下列各句中，没有语病的一项是（ ）

Scientists still wonder whether cloning will help or harm us and where it ____ us

She will tell us why she feels so strongly that each of us has a role ______ in making the earth a betterplace to live on. [ ]

The old couple tried to _____________some extra money for some purpose.