Final answer:
The young man would be charged with theft and drug possession.
Step-by-step explanation:
The young man would be charged with theft and drug possession.
Theft refers to the act of taking someone else's property without permission or consent, which is a criminal offense.
Drug possession refers to having illegal substances in one's possession, which is also a criminal offense. In this case, the young man traded the stolen diamond necklace for marijuana, making him liable for drug possession charges as well.