--- I think the environment is being worse and worse.
--- Yes, I really don’t know we can do about it.
A. which
B. whether
C. that
D. what
网友回答
A. which
B. whether
C. that
(答案→)D. what
解析：词义辨析。Which哪一个；whether是否；that那个；what什么。句意：我认为环境变得越来越差了。——是的，我们真的不知道关于这事我们能做什么。下文宾语从句中缺少逻辑宾语。故选D。