What do you recommend forbetter utilization of the result cache?

The result cache is enabled for the database instance.
Examine the following code for a PL/SQL function:

CREATE OR REPLACE FUNCTION get_hire_date (emp_id NUMBER) RETURN VARCHAR
RESULT_CACHE RELIES_ON (HR.EMPLOYEES)
IS
date_hired DATE;
BEGIN
SELECT hire_date INTO date_hired
FROM HR.EMPLOYEES
WHERE EMPLOYEE_ID = emp_id;
RETURN TO_CHAR(date_hired);
END;

You notice that results for the functions are not used effectively. What do you recommend for
better utilization of the result cache? (Choose all that apply.)

A.
Set the RESULT_CACHE_MODE parameter to FORCE.

B.
Increase the value for the RESULT_CACHE_MAX_SIZE parameter.

C.
Add a format mask parameter, such as RETURN TO_CHAR(date_hired, fmt) to GET_HIRE_DATE.

D.
Change the return type of GET_HIRE_DATE to DATE and have each session invoke the TO_CHAR function.