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.

Silver tarnishes as silver metal reacts with hydrogen sulfide, h2s, in the air. in this reaction, dark silver sulfide, au2s, covers the surface of silver. when silver is polished, this coating of silver sulfide can be removed from the surface. this makes the silver shiny again. enter the coefficients that balance the tarnishing reaction equation. (type 1 for no coefficient.)

Which process transfers heat from inside earth to its surface? convection currents in mantle pulling away of tectonic plates drawing in of tectonic plates convection currents in crust

Which of the following is a physical property flammability heat of combustion solubility and toxicity