Final answer:
The Storming stage is where interpersonal conflict occurs in a team, with members competing for roles and challenging each other's ideas.
Step-by-step explanation:
The stage of team development marked by interpersonal conflict as members become more proactive and compete for various team roles is b) Storming. This phase is characterized by competition and conflict in personal relations as the team members vie for positions and challenge each other's ideas and perspectives. It is a normal and necessary part of team growth, allowing members to eventually work together more effectively as they move on to the next stages, such as Norming and Performing.