After you realize that
0.00025 = 2.5·10^-4
= 250·10^-6 or 250 μ
= 250,000·10^-9 or 250,000 n
then it becomes a matter of semantics. Both A and D are correct representations, so choice B is incorrect.
Choice C present a dilemma. If you say it is correct, then there are 3 correct choices (A, C, D), not two, so C is incorrect.
If you say it is incorrect, then there are two correct answers (A, D), making choice C correct.
I'd probably choose C and try to avoid the argument with my teacher.
