铝罐还是塑料瓶？

recycle - v. to make something new from something that has been used before

dilemma - n. a situation in which one has to make a difficult choice

greenhouse gas emission - phrase, the release of gas that contributes to the warming of the earth's atmosphere by absorbing infrared radiation

carbon footprint - n. is the total amount of greenhouse gas emissions produced directly and in directly

smelt - v. to melt rock that contains metal in order to get the metal out

convenience - n. a quality or situation that makes something easy

biodegradable - adj. capable of being slowly destroyed and broken into very small parts by natural process