Who cannot purchase firearms?

The correct answer identifies categories of individuals who are legally prohibited from purchasing firearms based on federal and state laws. Specifically, minors, known drug addicts, and aliens fall into these categories due to concerns related to age, substance abuse, and citizenship status.

Minors are restricted from purchasing firearms to ensure that individuals who are not yet considered adults and may lack maturity or judgment do not have access to potentially dangerous weapons. Known drug addicts are prohibited because substance abuse can impair judgment and increase the likelihood of misuse or dangerous behavior. Lastly, alien status or non-citizenship can also restrict firearm purchases, particularly if those individuals do not have the legal right to possess firearms in the country where they reside.

This multifaceted approach to restricting firearm purchases aims to enhance public safety by preventing access to firearms by individuals who may pose a risk. The other options presented do not accurately reflect legal prohibitions on firearm purchases, thereby establishing why they are not correct. For example, having a high income or being under 30 years of age does not inherently disqualify individuals from purchasing firearms, nor does being registered or not registered to vote.