Recently, I have noticed that our student body has adopted a practice that should be avoided. Students discard a large amount of uneaten food during lunch. Everything thrown in the trash bins ends up in a landfill, which is a problem because the pollution and gases related to landfills can harm the environment. The writer uses the first sentence to:
O point out several effects of the problem.
O sum up the importance of the problem.
O propose a solution.
O express a viewpoint

(please help soon, doing exam! will take down your response if it's not helpful)