Consider classes A, B and C, where A is an abstract superclass, B is a concrete class that inherits from A and C is a concrete class that inherits from B. Class A declares abstract method originalMethod, implemented in class B. Which of the following statements is true of class C?

a. Method original Method cannot be overridden in class C—once it has been implemented in concrete class B, it is implicitly final.
b. Method originalMethod must be overridden in class C, or a compilation error will occur.
c. If method originalMethod is not overridden in class C but is called by an object of class C, an error occurs.
d. None of the above.

d. None of the above.