An object's motion changes
a.
when the forces acting on the object remain balanced.
b.
only if the object is at rest when a force acts upon it.
c.
only when a nonzero net force is applied to the object.
d.
all of these

The answer is D, because if the all of them will either stop the object in motion or move an object that is staying still.

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.

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