Which of the following cannot be used in identifiers?

A. Spaces

B. Digits

C. Underscores

D. Letters

Correct Answer is :

A. Spaces

Explanation

An Identifier can only have alphanumeric characters(a-z , A-Z , 0-9) and underscore( _ ). The first character of an identifier can only contain alphabet(a-z , A-Z) or underscore ( _ ). Identifiers are also case sensitive in C. For example name and Name are two different identifiers in C.