Final answer:
The most efficient method for Juan to manage new product development and task assignments is utilizing card view, which offers a visually organized way to oversee and reassign tasks quickly.
Step-by-step explanation:
Juan's most efficient option for managing the development of a new product and the assignment of tasks within his team would be option c) Juan needs to utilize card view to view by the assigned to contact column. This method allows for an organized and visual way to oversee who is responsible for what tasks, and makes the reassignment process relatively straightforward. By using card view, Juan can quickly and efficiently manage task assignment without creating separate filters or reports for each team member, and without waiting for email suggestions, which can be time-consuming and may lead to miscommunication.