1.从句意可以看出,C无疑是最准确的答案.
be eager for sth 渴望/渴求/争取...,指“以巨大的热情渴望实现愿望或达到目的
be enthusiastic for/about sth.对某事热心
be keen on/about sth 喜欢/喜爱...
be anxious for 渴望有(得到),指“热切地希望实现愿望,并因顾虑愿望落空而心情不安,感到焦虑的”
2.此题考察not...until..句型的倒装用法,所以我们必须先还原该句:
John couldn't go to school until his father was out of prison.
再倒装成:Not until his father was out of prison could John go to school.
所以我认为答案是C而不是A.
我认为楼主可能抄错题目,如果要选A,那么原题应该是:
It's not until his father was out of prison ____A___ to school.
a.that John could go
那么这考查的就是not...until...的强调句型了:
It's not until+某个时刻/从句+that+主句的肯定变化句式.
3.楼主应该又少抄了点什么.如果非要选C的话,那么在横线和I could't go on with my work之间加上一个that.
则此题考查的是so/such...that...的倒装句型了:
当“so/such ...that ...”结构中的so,such连同它所直接修饰的成分共同位于句首表示强调时,主句要进行部分倒装(that后面的结果状语从句不倒装).
如：So fast does he run that he is far ahead of others.他跑得如此快,以至于远远领先于其他人.
再如:To such an extent do the parents love their son that they have tried to satisfy every demand of his.父母俩爱子爱到了如此程度,以至于尽量满足他的任何要求.