Which of the following is not a valid identifier in C

Explanation

In C programming, identifiers are names given to variables, functions, constants, and other user-defined elements. Here's why return is not a valid identifier:Reserved keywords: return is a reserved keyword in C. Reserved keywords have specific meanings in the language and cannot be used as identifiers. Other examples of reserved keywords in C include int, for, while, and if.Valid identifiers:Must start with a letter (a-z or A-Z) or an underscore (_).Can contain letters, digits (0-9), and underscores after the first character.Are case-sensitive (e.g., age and Age are considered different identifiers).Cannot be the same as a reserved keyword