---- There is a lot of smoke coming out of the teaching-building there.
---- Really? It _____ be a fire, most probably.
| A．can | B．ought to | C．have to | D．must |
It is likely that these animals could be frightened， a sudden loud noise．
| A．being there | B．should there be | C．there was | D．there having been |
．—Steve come back because the window is open．
—Yes．but he _______left it open last night．
| A．must have；might have | B．might have；can’t have |
| C．can have；should have | D．might；must have |
_________we sleep together or apart is one of the biggest cultural differences, and only in western societies ______ the feeling that babies should sleep apart from their parents.
| A．No matter; it is | B．Whether; is it |
| C．No matter; there is | D．Whether; is there |
____ they are closest friends is not clear though they live together.
| A．That | B．If | C．What | D．Whether |
A tunnel was built under _____ was a lake a year ago.
| A．where | B．which | C．that | D．what |