UNION or DISTINCT()?

When deciding whether to use DISTINCT() or UNION in a query to remove duplicate rows, which of the following questions would you NOT ask yourself?

Answer the question

50 XP

Possible Answers

Is there an alternative method to using DISTINCT()?
press1
Will appending queries produce duplicate rows?
press2
Is there an aggregate function in the SELECT statement.
press3
Should I be thinking about duplicate rows because my queries never produce duplicate rows.
press4