12.1 Fill in the blanks in each of the following statements:
a) If a class contains at least one abstract method, it must be declared as a(n) ________ class.
b) Classes from which objects can be instantiated are called ________ classes.
c) ________ involves using a base-class variable to invoke methods on base-class and derived-class objects, enabling you to “program in the general.”
d) Methods in a class that do not provide implementations must be declared using keyword ________.
e) Casting a reference stored in a base-class variable to a derived-class type is called ________.
12.2 State whether each of the statements that follows is true or false. If false, explain why.
a) It’s possible to treat base-class objects and ...