25．Antarctic ____ we know very little is covered with thick ice all the year round. 　

A．which 　 B．where　　 C．that　D．about which

24．It's the third time ____ late this month. 　

A．that you arrive　　　 B．when you arrived

C．that you've arrived　 D．when you've arrived

23．This is just the place ____ I am longing to visit these years. 　

A．that 　 B．where　 C．in which　 D．to where

22．Mr Crossett will never forget the days ____ he spent with his various students. 　

A．when 　 B．which　 C．during which　 D．on which

21．The Second World War ____ millions of people were killed ended in 1945．

A．when 　 B．during that　　 C．in which　 D．which

20．Please lend us ____ tool as was used the other day.

A．same 　 B．as　　 C．the same　 D．that

19．He must be from Africa, ____ can be seen from his skin.

A．that 　 B．as　　 C．who　 D．what

18． ____ , the compass was first made in China.

A．It is known to all　 B．It is known that

C．We know all　　 D．As is known to all

17．I, ____ your good friend, will try my best to help you out. 　

A．who is 　B．who am　 C．that is　 D．what is

16．Each time ____ they met they would talked long hours together. 　

A．which 　 B．during　　 C．when　 D．不填