B . True. This statement will execute successfully because it has a single column in the SELECT statements combined with UNION, and the ORDER BY clause is referencing a valid column in the result set.
A is incorrect because it uses an ORDER BY clause with two columns, which is not allowed when the SELECT statements have only one column each. C is incorrect for the same reason as A; it references columns that do not exist in the result set. D is incorrect because it attempts to ORDER BY a second column, which does not exist in the result of the union.