Consider the following C$++$ variable names:

I.

II$.$

III.

IV$.$

V$.$

DISCOUNT

Which of the following options is correct?

Only I and IV are valid C$++$ variable names.

Only IV is a valid C$++$ variable name.

Only I, IV$,$ and V are valid C$++$ variable names.

Only III, IV$,$ and V are valid C$++$ variable names.