I won’t tell the student the answer to the math problem until he ________ on it for more than an hour．

A．has been working

B．will have worked

C．will have been working

D．had worked

________ to give up the bad habit．

A．He is impossible

B．He is possible

C．It is impossible for him

D．It is impossible to him

They are busy ________ their job．

A．doing

B．done

C．with doing

D．to do

When she ________, she will go to the big city．

A．graduated

B．graduates

C．will graduate

D．graduate

Ladies and gentlemen, please fasten your seat belts．The plane ________．

A．takes off

B．is taking off

C．has taken off

D．took off

The teacher told us water ________ at 100℃．

A．boil

B．boil

C．boils

D．is boiling

－Will you go to the party?

－Of course I will if ________．

A．I was invited

B．invited

C．having invited

D．I will be invited

－Do you remember ________ he came?

－Yes, I do, he came by car．

A．when

B．how

C．if

D．that

They have nothing ________ with one ________．

A．in commons; other

B．in common; another

C．in common; other

D．in common; others

The train was ________ to arrived at 11∶30, but it was an hour late．

A．about

B．certain

C．supposed

D．likely