Answer:
B and C
Step-by-step explanation:
A) wrong because valley has nothing to do with the envoiorment,
B) correct beacsue the guly coast has heavy pollution problems in their water which can affect the air and that air travels over mexico city
C) correct, a big population can equal alot of litter!
D) wrong theyre has been some left over from that but thats not really quite dealing with the question