In SQL, if you use SELECT DISTINCT, which of the following statements is true regarding the ORDER BY clause?
a) The ORDER BY clause can include columns that are not in the SELECT list when SELECT DISTINCT is specified.
b) The ORDER BY clause must include only columns that appear in the SELECT list when SELECT DISTINCT is specified.
c) The ORDER BY clause is ignored when SELECT DISTINCT is used.
d) The ORDER BY clause can only include columns that are aggregated in the SELECT list when SELECT DISTINCT is specified.