Human beings won't be aware of the importance of protecting the natural resources until they ________ them．

A．have run out of

B．will run out of

C．will have run out of

D．ran out of

The teachers told the students that they ________ to be useful men to the country．

A．were all expected

B．all expect

C．were all expecting

D．all expected

－Why are you late again?

－I ________ in the traffic, otherwise I would have got here half an hour ago．

A．am caught

B．caught

C．was caught

D．had caught

－I will come to see you again next month．

－Well, by the time you come again, I ________ for the USA．

A．would have left

B．will have left

C．have left

D．will leave

－Why didn't you come to the party last night?

－Well, I ________ but my sister was suddenly ill．

A．would

B．did

C．had

D．was going to

－What were you up to when your mother came back?

－I ________ the Sesame Street for a while and ________ some homework．

A．was watching; was going to do

B．was watching; doing

C．had watched; was going to do

D．have watched; was going to do

－Now that you were willing to take a risk, why not set out right now?

－I ________ that it is so adventurous．

A．don't realize

B．didn't realize

C．wasn't realizing

D．am not realizing

Whenever I go to visit my grandfather, he ________ books．

A．is always reading

B．will be always reading

C．has been always reading

D．always read

It is high time you ________ in bed now．

A．are

B．were

C．will be

D．would be

By this time next year he ________ from the college．

A．will be graduating

B．should be graduating

C．will have graduated

D．is graduating