Which of the Following Is Not a Valid Enumeration

Multiple Choice

Which of the following is not a valid enumeration?

A) enum class Person {ME, YOU, THEM};.
B) enum class Person {ME = 1, YOU = 2, THEM = 3};.
C) enum class Person {ME = 0, YOU = 0, THEM = 0};.
D) enum class Person {ME, YOU, ME};.