题目内容：

He didn't go to work because he was ill.(同义句)→He didn't go to work because of _____ _____.

优质解答

his illness.
解析：因为 because 是原因状语,所以后面接句子,引导原因状语从句.
而 because of 是一个短语,后面要接名词或名词词组形成介宾结构,这遵循的是是“介宾短语”.