The question asks to find the cardinality of the set $A$, where $A = \emptyset$ (the empty set).

The cardinality of a set is the number of elements in that set. Since the empty set contains no elements by definition, its cardinality is $0$.

The correct answer is: 0, as $\emptyset$ is the empty set, which contains no elements.

Would you like further clarification on the empty set or cardinality? Here are some related questions to deepen your understanding:

1. What is the difference between an empty set and a set with one element?
2. Can an empty set be a subset of another set?
3. How is the concept of the empty set used in real-world problems?
4. What is the cardinality of a set with multiple elements?
5. How do you represent the empty set in different contexts, such as in logic or programming?

Tip: In set theory, the empty set is denoted by $\emptyset$ or $\{\}$, and it is a subset of every set.