The correct answer to this question is All of the above. Character constants are single characters. The single character is enlosed in quotation marks, which are also single. Their purpose is to be representatives of characters in the set called execution character. This set is where the characters on the device execute them.
Examples of character constants are '4', 'L'. There are three types of character types, which are signed char, unsigned char, and just simply char. These characters are unable to be changed and are literal. Character constants are used in programming and should be treated just like variables.