Examine the description of the STUDENTS table: 
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)
正确答案:C,E
答案解析:有
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