The question of when the troops should leave would be decided by consensus. 

参考译文：部队应该何时撤离的问题将由大家共同决定。

主语：the question

修饰主语后置定语：of when the troops should leave

谓语：would be decided

状语：by consensus

以上结构为：介词短语of when troop should leave修饰前面的名词the question

of when the troops should leave 介词短语为介词of+连接副词when引导宾语从句。

What is the contact details of where you will be staying while in the UK?'

参考译文：当你在英国期间，你将住在哪里的联系详细信息是什么？

以上结构为：介词短语of where you will be staying修饰前面的名词 the contact details

of where you will be staying while in the UK 介词短语为介词of+连接副词where引导宾语从句。