To validate that the input is not a string before performing arithmetic operations, the function that should be used is the IsNumeric function.
Let's go through each option to understand why it is correct or incorrect:
Option A) IsArithmetic - This option is incorrect because there is no built-in function called IsArithmetic in most programming languages. This function does not exist.
Option B) IsNotString - This option is incorrect because there is no built-in function called IsNotString in most programming languages. This function does not exist.
Option C) IsNumeric - This option is correct because the IsNumeric function is commonly used to check if a value can be interpreted as a number. It returns true if the value is numeric and false if it is not.
Option D) IsString - This option is incorrect because the question asks for a function to validate that the input is not a string. The IsString function would be used to check if a value is a string, not the other way around.
Option E) IsValue - This option is incorrect because there is no built-in function called IsValue in most programming languages. This function does not exist.
The correct answer is C) IsNumeric. This option is correct because it allows you to validate that the input is not a string before performing arithmetic operations.