Final answer:
Professional or formal meetings are typically conducted to inform, solve problems through group exercises, and train or instruct attendees; eating and socializing are not primary reasons for these meetings.
Step-by-step explanation:
From the provided list, the reasons why a meeting might be held include the following: to inform participants about a particular subject, to solve problems through group exercise, and to train and instruct individuals in a certain area of knowledge or skill set. Eating and meeting with long-time friends, while possibly coinciding with the events of a meeting, are not primary reasons to hold a professional or formal meeting. Meetings are often convened to address and collaborate on issues, negotiate compromises, and successfully accomplish collective goals. These gatherings can also be essential for the sharing of information and for group decision making, particularly when collective behavior is involved, such as when a group of people gather to listen to an author speak. Moreover, issues such as decision-making processes under certain conditions, analyzing from multiple perspectives, and assessing the representativeness of samples, are frequently discussed and addressed during meetings.