The river is very deep. My mother warns me _________ in it.
Your English book is on the floor.Please________.
Susan used to________to school,but she is used to________to school now.
I think every student should go to school________,but some of them are always late.
To keep safe,everyone________to wear a seat belt in the car.
The little boy can’t understand what you said.________,he is only two years old.