What is the first line with a compiler error? 

A. Line R

B. Line S

C. Line T

D. Line U

E. None of the above.

class Mammal {} class Bat extends Mammal {} class Cat extends Mammal {} class Sat {} class Fur { } void clean () { } var bat= new Fur (); var cat= new Fur (); var sat = new Fur (); // line R // line S // line T // line U