Answer:
Formal and serious
Explanation:
Formal and serious because just look at the other options and cross them out. The first option is Funny and exciting I dont think that a eassy about the dangers air pollution would be funny or exciting. The second option Energtic and Happy the essay could be energtic but not Happy because you are writing about the dangers of air pollution. The last option is causal and informal if you are writing an essay you shouldnt be informal because the reader wont understand as much as it would if the essay was formal
