Is that man Mr.Zhang?
It____be him.He went to Beijing for a meeting yesterday.( )
can't
mustn't
needn't
I still remember my first teacher __________ we haven’t seen each other for many years.
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.