A carpenter needs to be sure that a frame he has built is rectangular. He knows that the opposite sides of his frame are congruent. Which additional fact would be sufficient to prove that the frame is a rectangle? A)

If two adjacent angles are supplementary, then the frame must be rectangular.

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B)

If the adjacent sides are also congruent, then the frame must be rectangular.

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C)

If opposite angles are congruent, then the frame must be rectangular.

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D)

If one angle is a right angle, then the frame must be rectangular.