表CUSTOMERS存在number类型的CUST_CREDT_LIMIT列。如下哪两个查询可以执行成功？CD A SELECT NVL(cust_credit_limit * .15, 'Not Available') FROM customers; B SELECT TO_CHAR(NVL(cust_credit_limit * .15,'Not Available')) FROM customers; C SELECT NVL(TO_CHAR(cust_credit_limit * .15),'Not available') from customers; D SELECT NVL2(cust_credit_limit,TO_CHAR(cust_credit_limit * .15),'NOT Available') FROM customers; E SELECT NVL2(cust_credit_limit * .15,'Not AvailabIe') FROM customers;