Select the choice that best completes the following sentence. simple machines a. cannot be combined to make compound machines. b. are tools that make work easier. c. reduce the amount of energy needed to do work. d. are made up of multiple moving parts.

How does a catalyst increase the speed of a reaction? a. the catalyst eliminates the activated complex stage, allowing products to form immediately. b. the catalyst lowers the energy level of the reactants, making it easier for them to react. c. the catalyst makes it easier for the activated complex to form, lowering the activation energy. d. the catalyst raises the energy level of the products, making the reaction finish sooner. reset next