This one came up in my interview. Remembering the entities/objects helped with my design, I would say make sure to add cardinality in all the designs. They also wanted to see how my database model worked. They threw curve balls in design to see whether this new entity would relate to the rest of the model. What's the new relationship, how would you adjust to the new cardinality. Hypothetical scenarios, and see where I would change the design.

Something to consider. Having cardinality initially would have made my interview smoother.