We′re doing a lot to protect our environment ,but it is not good enough,

题目

We′re doing a lot to protect our environment ,but it is not good enough,
We′re doing a lot to protect our environment ,but it is not good enough.So we should try { ]to look after it ,A;hard B;harder C; hardest详解谢谢

答案

B
给出的内容是,我们对于保护环境作了很多,可是还是不够好（not good enough）
后文是应该更努力,努力是try hard
根据上下文的关系,应该是更努力,加上比较级,变成try harder
注意hard本身就是副词,直接加er就可以了