We have realised that is much that can be done to help improve our environment.A. whatB.

问题补充：

We have realised that is much that can be done to help improve our environment.

A. what

B. it

C. there

D. one

答案：

A. what

B. it

(答案→)C. there

D. one

解析：考查there be结构。句意“我们已经意识到，为了改善我们的环境，我们能做的还有很多。”there be表示“有”，主语常是物；there is much“有很多（事情）”，后跟的是定语从句，修饰much。故选C。