1.这里的great简单来说就是形容词,很多、很大、很重要等等意思,need就是需要：
- We can see a great need to make our products better.（当务之急是要改进我们的产品）
- A great effort has been made to improve the quality of our society.（非常努力地改进我们的社团）
2.这两句根据配对的句子可有不同的意思,楼上两位的解释都通.
3.加了the便是有特定对象,没有加the便是泛指
4.Post-XXX 意即XXX之后,如Post-modernism后现代主义,Post-war战后
5.把这几个选项举例给你看：
- JOGN,you cannot go out to play until you FINISH your homework.
- JOGN,you cannot go out to play until your homework IS FINISHED.
- JOGN,you cannot go out to play until you HAVE FINISHED your homework.
第一句与第三句的分别：perfect form有强调作用.所以答案是2.若要使用3,便要加上被动形式been（has been finished）照前面几位的答案,就会变成作业自己完成自己.
6.这个句子我们拆开来看就很容易了
原来的句子 - We should take part in activities.
= 我们应该参加活动.
加入形容和规范 - We should take (an active) part in (all kinds of) activities.
= 我们应该（积极地）参加（各种）活动.
这样解释清楚吗?
