Question

初中英语语法的问题

forties 前的介词是in on of中的哪一个啊？
so as to\so that\in order to这些在用法上有什么不同啊？

Answer 1

先是你的第二个问题
in order to可以用在句首或句末，但so as to只能用在句末。
如：

He got up very early in order to/so as to catch the first bus.
In order to catch the first bus,he got up very early.（此时不能用so as to）
so as to 和in order to的汉语意思应该是一样的“为的是，为了”。它们的英语功能也是一样的，都可以用来引导目的状语。它们的不同之处就在于so as to 不能用于句子的开头，在句子开头只能用in order to.
另外，
1.in order to 一般用in order that加从句来替换；而so as to 一般用so that加从句来替换。in order that 可以在句首，so that和so as to 一样不能在句首。
2.当这两个短语后的不定式动词的逻辑主语和句子的主语一致时，“in order to , so as to +不定式”可以简化为“不定式”
In order to get to school on time,he got up earlier.这个句子可以表达为下列几种方式：In order that he could get to school on time,....
He got up earlier in order to get to school on time.
He got up earlier in order that he could get to school on time.
He got up earlier so as to get to school on time.
He got up earlier so that he could get to school on time.
To get to school on time, he got up earlier. （这种不定式有时可以表示目的以外的状语）

你的第一个问题：
前面应该是in
有一个固定的词组搭配是in one's …ies，意思是在某人的几十岁时，in forties应该就是在四十岁时

希望我的回答对你有一些帮助【楼主采纳我的吧=w=】

Answer 2

第一问：forties是用in 因为in one's forties意思是在某人40岁时
第二问：我简单点说，你做题时就不会错了。
so as to =in order to (在意思上），用法上:so as to 只能放在句中，而in order to 可以放在句首，也可以放句中。一般的选择题都是把横线画在句首，让你二选一。