It was lack of moneg,not of effort,_____ defeated their pian.

考察强调句，麻烦的是有插入语，所以解决方法是把插入语先去掉变成
It was lack of money ____ defeated their plan.
强调句的特点是，当强调结构被去掉后，所剩成分依然是句子，去掉It,was,___
后，句子是Lack of money defeated their plan.依然是句子，所以_____应填强调句中的that
针对其他答案，如果是非限定性定语从句，则前面应是完整句子，语意也要完整，如果理解为非限定性定语从句，则前面句子没有意义。 楼上太着急了，应该是想错了。

it was lack of money, not of effort, (which) defeated their plans.

关代 which 指前面的字 片语 子句时 要用 非限定子句

不能用 that 代替 [ who & which ]

怎么不能理解为非限制性定语从句，谢谢