If R = {(1, y), (1, z), (3, y)} then R power (-1)= ___________.

• A. {(1, a), (y, z)}
• B. {(y, 1), (z, 1), (y, 3)}
• C. {(y, a), (1, z), (3, y)}
• D. {(y, a), (z, a), (3, y)}