java question

Consider the following program where Dog is derived from Animal and Wolf is derived from Dog: public class HelloWorld{ public static void pName (Animal a) { } public static void pCall(Wolf w) { } public static void main(String[] args) { Animal a1 = new Animal(); Animal a2 = new Dog(); Dog d1 Dog d2 Wolf w = new Dog(); = new Wolf(); = (Wolf) d2; //the statement goes here } } Which of the following statement causes compilation error when inserted into the program above? Select one: a. pName(d1); b.pCall(w); c.pName(a1); d.pCall(d2); e.pName(a2)