We all know that learning a foreign language _________time and effort．
A．requires B．drops
C．greets D．develops
If you put your heart into it，_________ is impossible．
A．anything B．something
C．everything D．nothing
You never play the piano well _________you practice it again and again．
A．if B．since
C．unless D．after
一Did you catch what our head teacher said?
一Sorry，I _________ a phone．
A．will answer B．am answering
C．have answered D．was answering
一I don't know _________ she can't go hiking with us．
一She has to do her homework．
A．when B．if
C．why D．how
一_________will the fog and haze last?
一I've no idea．there is no sign of an end．
A．How soon B．How far
C．How long D．How often
