同学你好，该知识点来自沪江网校《英语零基础直达大学六级【3年随心畅学班】》的课程，想要更系统的学习，欢迎进入课程学习。不仅可以和更多的同学一起学习，而且还有老师、助教随时的学习指导和知识点解答哦。

同学你好~
it在这里是形式宾语，真正的宾语是to keep Eric in hiding
their duty是宾补。
If he thought it his duty to arrest me, he'd do it like a shot.
如果他认为逮捕我是他的职责，他会毫不迟疑地去做。
Only a third of these households thought it reasonable to meter water
这些家庭当中只有三分之一认为用水表计量是合理的。

sb find/ believe/ think/ feel/ consider/ make + it +n+to do
He makes it a rule never to borrow money.（他立志决不向别人借钱。）

祝同学学习进步~