The students _____ the bus and walk across the bridge _____ the river. 

Don’t keep silence! The head teacher is ___________a lot about that. 

We should ________ ‘Thank you’ when we borrow something from someone.

For most people, it’s very difficult to _____ air on the top of Qomolangma.

——What’s your mother?——She_________ a teacher, but now she is a doctor.