Abstract Classes and Class Members的用法和样例：
- There are several attributes you can apply to classes and class members that modify their behavior and visibility.
- Inheritance modifier that allows for definition of classes and class members, but does not allow implementations to be given.
- Class is an abstract class and cannot be instantiated.
- Note that if the parent class is an abstract class and contains at least one abstract member, those members will automatically be implemented in non-abstract inheriting classes.
- Laura: It's a football game between our class and class two.