Which of the following statements is false?
a. because a wildcard is a type-parameter name, you can use it as a type name throughout a method's body.
b. a wildcard-type argument is denoted by ? ,
c. which represents an "unknown type." if a wildcard is specified without an upper bound, then only the methods of type object can be invoked on values of the wildcard type.
d. wildcard type arguments enable you to specify method parameters, return values, variables, and so on, that act as supertypes of parameterized types.