Which digit is its own square and its own cube?

Answer: D. Both B and C

0 x 0 = 0 and 0 x 0 x 0 = 0, while 1 x 1 = 1 and 1 x 1 x 1 = 1. So both 0 and 1 are equal to their own square and cube; 2 is not, since 2^2 = 4.

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