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A.SELECT COUNT(*) FROM employees WHERE last_name='Smith';
B.SELECT COUNT(dept_id) FROM employees WHERE last_name='Smith';
C.SELECT DISTINCT(COUNT(dept_id)) FROM employees WHERE last_name='Smith';
D.SELECT COUNT(DISTINCT dept_id) FROM employees WHERE last_name='Smith';
E.SELECT UNIQUE(dept_id) FROM employees WHERE last_name='Smith';

A.A single row subquery can retrieve only one column and one row.
B.A single row subquery can retrieve only one row but many columns.
C.A multiple row subquery can retrieve multiple rows and multiple columns.
D.A multiple row subquery can be compared using the ">" operator.
E.A single row subquery can use the IN operator.
F.A multiple row subquery can use the "=" operator.