What is true of using group functions on columns that contain NULL values?（）

• A、Group functions on columns ignore NULL values.
• B、Group functions on columns returning dates include NULL values.
• C、Group functions on columns returning numbers include NULL values.
• D、Group functions on columns cannot be accurately used on columns that contain NULL values.
• E、Group functions on columns include NULL values in calculations if you use the keyword INC_NULLS.