human
Question: The following mathematical expressions represent four different concentrations of a chemical solution to be used in a science experiment. Which one is equal in magnitude to 1/1000?

Choices:
A) 1.0 x 10^3
B) 1.0 x 10^4
C) 1.0 x 10^-3
D) 1.0 x 10^-4
gpt
The correct answer is 2: 1.0 x 10^-3.