ERD relationship to depict one head coach

• A. Optional One
• B. Optional Many
• C. Mandatory One
• D. Mandatory Many

Answer: (C)

In an ERD, the numbers describe how many instances of one entity can be linked to a single instance of the other. To depict that each team has exactly one head coach, you use a mandatory one on the relationship from Team to Head Coach. This means every team must be linked to exactly one head coach—existence is required for the team, and the association is limited to one head coach per team. It’s not optional because a team cannot exist without a head coach, and it’s not many because the scenario specifies a single head coach per team. Choosing a pattern that allows no head coach or multiple head coaches would not match the idea of “one head coach” per team.