What is the result of using `parseInt()` on a string of digits?

Using parseInt() on a string of digits converts that string into an integer value. The function processes the string, interpreting the initial characters as a valid integer up until it encounters a character that is not a digit. For example, if you pass the string "123" to parseInt(), it will return the integer 123. If the string starts with non-numeric characters, parseInt() will return NaN (Not-a-Number). Thus, when it comes to strings of digits, the primary function of parseInt() is to convert such strings into their integer representation, which makes option C the correct choice in this context.