Why do a comet's two tails often point in different directions?

List four observations that indicate that a chemical reaction may be taking place

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 characteristics can be used to differentiate star systems? check all that apply.