6 had learned ( by the end of last term 到上学期末为止,要用过去完成时)
7 Is chatting ( 根据HE ISN‘T HERE,可知他正在做某事)
8 are talking ( LISTEN 开头,后面的动词要用现在进行时)
9 had happened ( 主句是一般过去时ASKED,从句要用相应的过去时
10 was stolen ( MOBILE PHONE作主语用被动语态
11 interviewed ( JUST NOW 刚才,一般过去时
12 will leave 或 is leaving { 用现在进行时表示将要发生的动作}( IN TEN MINUTES 十分钟后,用于一般将来时
13 have learned ( FOR …… ,现在完成时
14 joined ( IN 1997,已过去时,用一般过去时
15 was picking ( WHEN 引导的从句,当一个动作发生,另一个动词正在进行
16 cost ( 根据句意只有花了才知道要多少钱,故要用一般过去时,COST 的过去式与原形相同
17 had begun ( 动作发生在got to 之前,故用过去完成时
18 goes ( 主语是三单,一般现在时,故谓语动词go 要加es
19 seems ( 主语是三单
20 are playing ( LOOK 开头,后面的动词要用进行时,主语是复数,故BE 要用are)