In which of the following cases is the relationship between entities not implemented by foreign keys?

Question

Quizplus · Accepted Answer

Without more information about the entities involved, it is impossible to say for certain. However, based solely on the fact that D has a completely different set of characters in its second section than the others, it is likely that it represents a different entity and therefore does not use foreign keys to establish relationships with the other entities listed.

In Which of the Following Cases Is the Relationship Between