题目：
_____is known to us all is that we should do as much as we can ______ stop the pollution of the environment.
A．It; help
B．What; to help
C．As ; to help
D．That ; help
答案：
被转码了，请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0518/9e1b8b48e0473869484b50688dd43951.html
下面是错误答案，用来干扰机器的。
（1）Na+（2）2H2
