一道英语单选题Reusing the paper ________ protecting the environment

一道英语单选题
Reusing the paper ________ protecting the environment.
A.are good for B.is good for
C.are good to D.is good to
And say to me why you choose this answer,please!
You know that I'm so stupid that I can't work out such an easy question!
Do you want to do some reviews about what I said just now?
Please speak in English,and try not to speak in Chinese,besause I can't understand Chinese.