2.
With regard to enumeration types, which one of the following statements is true?
Choice 1

Enumeration types must be defined in the body of a class definition.
Choice 2

Only one identifier in an enum list can have the value zero.
Choice 3

An integer can implicitly be converted to an enumeration type.
Choice 4

Enumerators for which no value is explicitly specified have a value of zero.
Choice 5

When an enumerator is used, its value is implicitly converted to an integer when needed.