求助英语语法高手1.Starting around 7000 B.C., and for the next four t

求助英语语法高手
1.Starting around 7000 B.C., and for the next four thousand years, much of the Northern Hemisphere experienced temperatures warmer than at present.为什么有个介词at.
2.It is my belief that many individual characteristics-including age,gender,expectations,experience and temperamemt.为什么age gender 没有s expectation有s?
3.Education in a modern economy is one of the conditions to achieving economic growth.为什么是achieving?
4.Overworking is linked to many adverse health effects,including profound fatigues,back pain,general anxiety,headaches.为什么fatigue和headache要加s?为什么pain和anxiety不加?两个疑问啊!也就是问的什么时候加S
5.Those who are from a working-class backgound are more likely to experience stress.
为什么一个句子有两个谓语are?
6.Automobiles have been mass-produced and sold at a price the average could afford.
为什么the前面没有that?
7.宾补和后置定语有什么区别?
8.most children seem to be.为什么不是seems?
9.A significant number of young people have been leacing the countryside for urban areas.为什么是介词for而不是to?
10.therefor和thereby用法一样么?我知道therefore不是连词 不能连接句子,thereby呢?
11.This is a fast changing world, in which English monolinguals are in danger of being left behind.为什么要加在which前加个in?which不是能指代前面的world么?这个请详细解释下
12.从句中需要注意的技巧,比如that在定语从句做宾语时可省略之类的,越详细越好

1.Starting around 7000 B.C., and for the next four thousand years, much of the Northern Hemisphere experienced temperatures warmer than at present.为什么有个介词at.
答：at present 固定搭配,时间状语,类似于at the moment.这是是比较句,than 后面省略了(相同的）主语和谓语：than the Northern Hemisphere experienced temperatures at present.
2.It is my belief that many individual characteristics-including age,gender,expectations,experience and temperamemt.为什么age gender 没有s expectation有s?
答：有个短语：live up to one's expectations是指“不辜负某人的期望”,用的也是复数
可能这是指期望的东西吧,就像：
experience , 还是根据意思,做经验,不可数,经历就可数
difficulty 困难,不可数, 困难的事情,就可数.
3.Education in a modern economy is one of the conditions to achieving economic growth.为什么是achieving?
4.Overworking is linked to many adverse health effects,including profound fatigues,back pain,general anxiety,headaches.为什么fatigue和headache要加s?为什么pain和anxiety不加?两个疑问啊!也就是问的什么时候加S
5.Those who are from a working-class backgound are more likely to experience stress.
为什么一个句子有两个谓语are?
6.Automobiles have been mass-produced and sold at a price the average could afford.
为什么the前面没有that?
7.宾补和后置定语有什么区别?
8.most children seem to be.为什么不是seems?
9.A significant number of young people have been leacing the countryside for urban areas.为什么是介词for而不是to?
10.therefor和thereby用法一样么?我知道therefore不是连词 不能连接句子,thereby呢?
11.This is a fast changing world, in which English monolinguals are in danger of being left behind.为什么要加在which前加个in?which不是能指代前面的world么?这个请详细解释下
12.从句中需要注意的技巧,比如that在定语从句做宾语时可省略之类的,越详细越好
再问： 第二句 age gender怎么不加s 不也是可数的么
再答： 字数有限，写在博客里 http://hi.baidu.com/凌雪1989/blog/item/4bb58d1e6c2ee412c93d6d0c.html