20．Only when 1 was fourteen　　　　 the importance of study．

A．I realized　　　　 B．did I realize　　　　 C．had I realized　　　　 D．I had realized

19．Water，　　　　 is a clear liquid，is widely used in our everyday life．

A．which　　　　　 B．that　　　　　　　 C．what 　　　　　　　　D．who

18．　　　　 8 gold medals in the National Aquatics Center，the US swimmer Michael Phelps has become the best known Olympic champion ever．

A．To win　 　　　　B．Having won　　　　 C．To have won　　　　 D．Winning

17．Can you make sure　　　　 the MP4?

A．where James had lint　　　　　　　　 B．where had James put

C．where James has put　　　　　　　　 D．where has James put

16．一Let’s go shopping，shall we?

A．It’s my pleasure　　　　　　　　　　 B．It doesn’t matter

C．Not at all　　　　　　　　　　　　　 D．OK，let’s go