Some exchange students _______ with their host families this time yesterday.( )
are chatting
will chat
were chatting
have chatted
His office is on the top of the tall building. You should take a lift to the floor.( )
first
thirtieth
thirty
thirteen
The air pollution is very serious in our city. Something about it now.( )
can do
must do
was done
must be done
The Great Wall is a place of interest. All of us there before.( )
has been
have been
has gone
have gone
Would you like to play table tennis with me this afternoon?
I'd like to. I'm afraid I have no time.( )
So
Or
But
And
Communication is a bridge the young and the old.( )
across
through
between
among