You have a class hierarchy including a base class and two derived classes.
public class A { }
public class B extends A { }
public class C extends A { }
Select all incorrect assignments.
A a1 = new C(); // (1)
A a2 = new A(); // (2)
B b1 = new A(); // (3)
B b2 = new B(); // (4)
B b3 = new C(); // (5)
C c1 = new A(); // (6)