It took thousands of years to form this canyon. what most likely caused the formation of the canyon? a) a volcano b) an earthquake c) a rushing river d) a tectonic shift

The correct answer is option C, a rushing river

Explanation:

Canyons are formed as of the erosional activities of both wind and water affecting a huge plateau, mountain or hill. These plateaus, mountains, and hills are formed due to tectonic movements.  

During the course of time, snow on the plateau melts and pull down half a million tons of sediments along with it. This sediment carrying river cuts the plateau thereby forming the Canyons

the dark variety, as they are not visible on the dark tree barks

explanation:

it provides an alternative energy pathway for the reaction to proceed.

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.