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 _______.