2.时间状语：by the time of; by the end of+时间短语;by （将来）the time+从句（将来）
3.基本结构：主语+be going to/will/shall + have+p.p（过去分词）+其他
4例句:By the time you get back, great changes will have taken place in this area.
十、现在完成进行时
1.概念：表示从过去某一时间开始一直延续到现在的动作。这一动作可能刚刚开始，也可能仍在继续，并可能延续到将来。
2.基本结构：主语+have/has +been +doing+其他 3.时间状语：since+时间点，for+时间段等。 4.例子：I have been sitting here for an hour. The children have been watching TV since six o'clo