Giancarlo sets up 5 test tubes: pH 3, pH 5, pH 7, pH 9, and pH 11. Each test tube has 50 g of the pH buffer solution, 10 g of the enzyme DNA polymerase, and 50 g of the enzyme's substrates (a short piece of a DNA chromosome and free RNA nucleotides). He measures the activity rate of DNA polymerase in each test tube by measuring how many copies of the DNA chromosome it produces as products of its reaction. Which statement BEST describes the components of Giancarlo's experiment?