A : True - The TO_CHAR function is used correctly here to convert the numeric value to a string, and NVL handles the case where cust_credit_limit might be NULL. The expression inside NVL computes 15% of the credit limit or displays 'Not Available' if the credit limit is NULL. The syntax is correct.
B : False - The NVL2 function requires three parameters: the expression to check for NULL, the value to return if it's not NULL, and the value to return if it is NULL. The given usage lacks the required parameters and syntax.
C : False - The NVL function expects both parameters to be of the same data type. Since the second parameter 'Not Available' is a string, it causes a data type conflict with the numerical result of the first parameter.
D : False - The keyword SELECT is misspelled as SLECT, making the syntax incorrect.