explain Legal Drinking Age, 18 or 21??

We have to find a political situation and be bias and give both sides pro and con, as well as a possible compromise that would satisfy both sides. I chose drinking age from 21 to 18. I would like to include things about not changing it due to physical and psychological aspects such as the body is still growing, etc. And for the changing, possibly something to include that you can go to war and protect your country, or serve a life sentence (tried as an adult) but you can\’t drink. 6 minimal secondary sources. Please read the attached instruction sheet.