made things worse he said was that his roommate never took part in any of the cleaning

问题补充：

made things worse, he said, was that his roommate never took part in any of the cleaning work．

A. What

B. Which

C. That

D. Who

答案：

(答案→)A. What

B. Which

C. That

D. Who

解析：考察主语从句。What引导起主语从句what made things worse并在句中作主语，结合句意可知A正确。句意：他说：让事情更糟糕的是他的室友从来不参加清洁工作。