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 derived-class objects similarly.

b) All methods in an abstract class must be declared as abstract methods.

c) Attempting to invoke a derived-class-only method through a base-class variable is an error.

d) If a base class declares an abstract method, a derived class must implement that method.

e) An object of a class that implements an interface may be thought of as an object of that interface type.