1、D。not so as to
2、C。“that is ” can be omitted without influencing the whole meaning。
In C,the word“it”is the problem。However, this chioce is better than others。
3、B
justag:
1、I do choose B of question 3。In my last page,I just want to explain why I did not choose D
2、According to question 1, I agree with your opinion that the right expression is “not so as to”