I see.
The correct way to write these is
A: 3^-2 * 3^ - 2 = 1/9 * 1/9 = 1/81 and this one is fine.
B: 3^-4 = (1/3)^ 4 = 1/3 * 1/3 * 1/3 * 1/3 = 1/81 and this one works.
C: (3^-2)^2 = (1/9)^2 = 1/81 and this one also works.
D: No matter how you interpret this, it is not going to equal 1/81. I think it might be written as -(3)^2 * - (3)^2 = - 9 * - 9 = 81 which is not correct.
Answer: D
