Who is more likely to give in to peer pressure and start substance abuse? A.
Katrina, who has been feeling depressed and upset lately but can discuss her problems with her older sister.
B.
Marc, who just joined a new school and is finding it hard to make friends, especially because his parents are away a lot.
C.
Becky, who saw her favorite actor taking cocaine in a movie and thinks it's cool. Her best friend disagrees and warns her not to copy him.

B.  Marc, who just joined a new school and is finding it hard to make friends, especially because his parents are away a lot.

Explanation:

Marc is most likely to give into peer pressure because his tendency to please his friends is higher compared to Katrina and Becky. The fact that Marc's parents are not present most of the time to guide him or give him an advice will make him at a higher risk to fall prey to peer pressure.

Once Marc finds a set of friends, he'll be encouraged to conform/adapt to their rules in order to keep the relationship. This means that even if his friends will use illegal drugs, Mark has a high probability to follow them. This is also because he doesn't have anyone to confirm whether his actions are good or not because his parents are away and he doesn't want to be lonely in the new school.

it should be

abuse, both physical and emotional. messes with your head. makes you feel like nothing, no matter what anyone else tells you