안녕하세요!

1. air pollution is a bigger concept that encompasses CO2 gas emissions.

예를 들면 sports랑 baseball 관계랑 비슷한거죠.

baseball is a type of sport, but not all sport is baseball.

CO2 is a type of air pollution, but not all air pollution is CO2.

combustion reactions can result in many other gases released, aside from CO2,

for example, sulfur dioxide can be produced, mercury particles can be released, particulate matter can fly off, etc 

and these can cause entirely different types of environmental problems.

그러니까 reduced air pollutant가 발생된다고 써도 괜찮아요. 

이게 꼭 CO2만 한정해서 말하는게 아니니까.

2. 이건 문제를 다시 봐야할거 같은데요? 

문제에선 하나의 장점, 하나의 단점을 말하라고 했으니

does not provide a consistent source of energy라고 하면 

단점을 쓰는게 맞죠? 만약 그랬다면 괜찮은 답변이에요. 문제없어요.

열공하시고 또 질문이 생기면 게시판에서 만나요! :D