The answer is A. Peer influence.

Peer influence refers to the impact that people of the same age or social status can have on an individual's thoughts, feelings, and behaviors. This influence can be both negative, leading to behaviors like drinking alcohol, and positive, encouraging beneficial choices.

Let's look at why the other options are less suitable:

B. Social group: While peer influence often occurs within social groups, the term itself doesn't specifically describe the influence exerted. A social group is simply a collection of individuals.
C. School performance: This refers to a student's academic achievements and is not directly related to the encouragement of behaviors like drinking alcohol or positive choices in a general sense.
D. Body shaming: This is the act of criticizing or humiliating someone based on their physical appearance and is not related to the broader influence of peers on various behaviors.