Examine the description of the STUDENTS table: STD_ID NUMBER(4) COURSE_ID VARCHARD2(10) START_DATE DATE END_DATE DATE Which two aggregate functions are valid on the START_DATE column?（）
- A SUM(start_date)
- B AVG(start_date)
- C COUNT(start_date)
- D AVG(start_date, end_date)
- E MIN(start_date)
- F MAXIMUM(start_date)