It was not until dark ___ he found ___ he thought was the correct way to solve the problem.填that，when，what（这是道选择题，我倒是选对了，但是只凭语感而已。希望有人帮忙解释一下原因，尤其是not until，until提前的句式）~~~英语都没救药了...
热心网友
that，what首先，这仍然是一个强调句型，It be …… thatwhat he thought 是一个主语从句what he thought was the correct way to solve the problem 是found 的宾语从句 非强调句型为：he didn't find what he thought was the correct way to solve the problemuntil night.
热心网友
that;what 是吗？如果是，那我解释喽！It was not until ……that 意思是直到……才。这句话的意思是“他直到晚上才找到他认为解决问题最好的办法。”what引导宾语从句作found的宾语，它本身在从句中作thought的宾语。