A. Interaction diagrams are at their best when they deal with one main design flow and not multiple variants that can happen
B. Interaction diagrams are good at designing part or all of one use case’s functionality across multiple objects
C. Interaction diagrams allow the analyst to show iteration and conditional execution for messaging between objects
D. All of the mentioned

Explanation: Interaction diagram is used to describe some type of interactions among the different elements in the model. So this interaction is a part of dynamic behaviour of the system.