Which ActionScript 3.0 data type serves as the base class for all class definitions?

The choice of Object as the correct answer comes from the fundamental structure of ActionScript 3.0, which is an object-oriented programming language. In ActionScript 3.0, the Object class serves as the base class for all other classes, making it a crucial element in the language's hierarchy.

Every class that you define in ActionScript 3.0, whether it is a built-in class or a custom class, ultimately derives from the Object class. This means that they inherit the properties and methods defined by Object, which is why it acts as the foundational class. For instance, any custom class you create can utilize methods like toString() or valueOf(), which are part of the Object class.

In contrast, other options like Array, Int, and Function are specific data types or structures that do not serve as a base class for all class definitions. While they are integral to various operations and functionalities within ActionScript, they do not share the foundational role that Object has in the class hierarchy. Understanding this structure is essential for anyone working with ActionScript as it enhances comprehension of how different types interact and inherit properties in the language.