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?

  Options: 
 A. 1.0 x 10^3
 B. 1.0 x 10^4
 C. 1.0 x 10^-3
 D. 1.0 x 10^-4 
Answer: C