宾语从句，不过这种表达挺少见的，通常是how workable

很常见

这个句型在不同场合见过很多次了

这个短语歪果仁非常常用，以下是随便在国外网站给你COPY 的。。。
9.
It is unclear to what extent America understands or is willing to accept this.
ECONOMIST: Cuba
10.
But to what extent is it - or has it ever been - properly enforced?
BBC: The many faces of Sharia
11.
To what extent will up-and-coming economies such as China and India be asked to rein in their skyrocketing emissions?
NPR: Climate Experts Mull Payment to Stop Deforestation
12.
To what extent Sears and Kmart themselves drift together as brands remains to be seen.
ECONOMIST: Merger at the mall | The
13.
To what extent is the useful vitality of that detail inseparable from its historical reality?
NEWYORKER: Broken Record
14.
It will help you to determine to what extent you want to move resources to the cloud.

词典都有这个句子 你说人家造次