City air is very dirty， so it would be wise ______ you to wash your hair often.— I know， but it is not easy ______ me to do that every day.

Do you know _______ girl over there— Yes, she is my best friend.

下列各句中，没有语病的一项是（ ）

The detective and his assistant have begunto the mysterious murder.

It was announced that only when the fire was under control ______ to return to their homes. [ ]