答案：C

此题容易误选A，受空格前逗号的影响，误认为这是一个非限制性定语从句，从而误选了A。其实，此题最佳答案为C，整个句子为一个 it was…that… 强调句，被强调成分为 lack of money, not of effort。由于句中插入 not of effort这一结构，干扰了许多同学对 it was lack of money that defeated their plan这一强调句的认识和分析。