I would assume that 512 is a whole number and the choices giver have the first digit as the coefficient and the second digit as the exponent.
A.) 92 ⇒ 9² = 9 x 9 = 81
B.) 44 ⇒ 4⁴ = 4 x 4 x 4 x 4 = 256
C.) 28 ⇒ 2⁸ = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256
D.) 29 ⇒ 2⁹ = 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 512
The correct answer is D. 2⁹ is how 512 is written as a power of a number.