Answer:
The cardinality symbol Z indicates zero or one child
Step-by-step explanation:
Cardinality is an element for specifying the number of entity instances included in a relationship. If you consider the cardinality for the link between the entities class and course, you will realize that somebody can teach the same course in different classes and viceversa. This represents a nonidentifying relationship. In the case of the letter Z, it indicates that there is either zero or just one child.