Please choose the correct answer to the 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?

Answer1: 1.0 x 10^3 Answer2: 1.0 x 10^4 Answer3: 1.0 x 10^-3 Answer4: 1.0 x 10^-4

Answer format: answer1/answer2/answer3/answer4