Which best describes the smog in Los Angeles?

A it is a negative effect of the regions. Focus on cutting down forest for different purposes.
B it is a positive effect of the regions. Focus on cutting down forest for different purposes.
C it is a positive effect of the regions. Focus on using the automobile as the main form of transportation.
D it is a negative effect of the regions. Focus on using the automobile as the main form of transportation.

D it is a negative effect of the regions. Focus on using the automobile as the main form of transportation.