Keywords are reserved words with predefined meanings in C. Because the language reserves them for specific purposes, they cannot normally be used as programmer-defined identifiers.
Programming in C MCQ - Keywords & Identifiers
int is a C keyword used to specify an integer type. The other choices are not reserved C keywords and can be used as identifiers when naming rules permit.
switch is a C keyword used in selection or branching constructs. The other listed words are not C keywords.
float is a reserved C keyword that denotes a floating-point type, so it cannot be used as a variable name. The other names can be identifiers if otherwise valid.
A C identifier may be formed using letters, digits and the underscore character. Its first character must satisfy the identifier-start rule rather than being a digit.
