Which of the following statements about polymorphism are true? (Choose all that apply)
A reference to an object requires an explicit cast if referenced with a subclass, A is incorrect.
Because of polymorphic parameters, if a method takes the superclass of an object as a parameter, then any subclass references may be used without a cast, so B is correct.
All objects extend java.lang.Object, if a method takes that type, any valid object, including null, may be passed; C is correct.
Some cast exceptions can only be detected at runtime, D is incorrect.
Because of polymorphism, a public instance method can be overridden in a subclass and calls it via reference to superclass, so E is incorrect.