Final answer:
The best description for A being immediately next to B is 'A and B are adjacent,' indicating they are in close proximity with no space separating them.
Step-by-step explanation:
When A is immediately next to B, it indicates that there is no space between them; they are in close contact. The statement that best describes this situation is A) A and B are adjacent. This implies that they are next to each other without any separation, which is consistent with proximity, a term that relates to the closeness or nearness of objects in space.
In the various scenarios presented, such as A not moving while B moves at 24 m/s or both A and B moving together at 8 m/s in the +x-direction, these describe their motion rather than their proximity. The other options B) A and B are separated by one person, C) A and B are not in close proximity, D) A and B are far apart, and E) A and B are on opposite ends, do not accurately represent the given relationship between A and B as they imply some form of separation.