the biggest () in the world may be the pollution 括号内填Apuzzle B problem C matter为什么

the biggest () in the world may be the pollution 括号内填Apuzzle B problem C matter为什么
the biggest () in the world may be the pollution 括号内填Apuzzle B problem C matter
为什么

the biggest () in the world may be the pollution 括号内填Apuzzle B problem C matter为什么
B
翻译：全世界最大的（）可能是环境污染
括号里的肯定是不好的东西啦~puzzle谜题,matter 困扰 problem 问题.这样的话污染一般来说是难以解决的问题,所以选B

the biggest (B) in the world may be the pollution 括号内填Apuzzle B problem C matter
世界上最大的问题可能是污染

B