Which example best illustrates the process of natural selection?

a
Giraffe necks varied in length and all offspring had an equal chance of survival.
b
Giraffe necks varied in length and the shorter neck giraffes were at a disadvantage.
c
Giraffes with the short necks migrated to locations best suited for their neck lengths.
d
Giraffes stretched their necks to reach food, and resulting offspring had longer necks.

d

Explanation: giraffe strenched their necks to reach food and resulted into their offspring having longer necks

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.