Multiple choice

Which one of the following is not a valid identifier?

  1. Ident

  2. Auto

  3. BigNumber

  4. G42277

  5. Peaceful_in_space
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In C, certain keywords are reserved and cannot be used as identifiers. 'auto' is a storage class specifier keyword (for local variables with automatic storage duration), so it cannot be used as a variable name. Options A, C, D, and E are all valid identifiers under C naming rules (letters, digits, underscores, not starting with a digit).

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