당연하지만, 밀집 되어 있을수록 매연 배출은 줄어듭니다 -- 잘 생각해보면 그닥 찾기 어려운 것도 아니지요.
And the correlation, of course, is that denser places tend to have lower emissions -- which isn't really all that difficult to figure out, if you think about it.