I think it essential that...为什么不用 I think it is..

I think it essential that...为什么不用 I think it is.. 中学英语学习中的一个小小语法点,不大懂,例句：I think it essential to reserve air tickets这一类句子中都用 it 作形式宾语请问：为什么这个例句不能改为“I think it is essential ... 感觉读来也挺顺啊. Before giving my opinion,I think it is essential to look at the argument of both sides. I think it----question---- Think it over ,I think it's I think it quite essential that your child ___ a foreign language at school.A．must learnB．learnsC．learnedD．learnD始终没搞明白这个宾语从句中的动词为什么用原形? I think it _____________your jacket I think you do it I it think is right I think it's impossible I think it must___Lucy's. it is not what i think you think but what you think i think you think. it's dark.I think it ( )soon I do that sometimes I think it I think i'll market it 翻译 i think i got it意思 Don't you think it essential that every resident of Nanjing should spare no effort to make contributions to Nanjing 2014 Youth Olympic Games?全句意思知道spare no effort 怎么翻译?另外it essential 怎么翻译 I think i'll take it=I（）think i'll take it=I()think it()rain