The world is changing with every second;and China,______ too,with every second.( )
A.is changingB.had changed
C.changed
They have been friends __________ they were at primary school.
I’ll go to visit my uncle in England ________ the winter holidays start.
The mobile phone has changed people’s life a lot ________ it was invented.
Getting enough sleep is good for _______ health _______ study.
— Hey, boy. You can’t cross the street now. You have to wait _______ the traffic lights turn green. — Oh, sorry and thank you.