If R = {(1, 2),(2, 3),(3, 3)} be a relation defined on A= {1, 2, 3} then R . R (= R2) is

• A. {(1, 2),(1, 3),(3, 3)}
• B. R itself
• C. {(2, 1),(1, 3),(2, 3)}
• D. {(1, 3),(2, 3),(3, 3)}