What might cause scientists to change a scientific theory?
a. some people disagree with it
b. it covers too broad a topic
c. new evidence contradicts it
d. it is too old

The correct answer will be option-C.

Explanation:

A scientific theory is a well-substantiated prediction or an idea which explains the natural process or phenomenon in depth. A scientific theory is made on the basis of facts and evidence of the previous research and theories.

The scientific theory is the elaborate explanation of any hypothesis which could be changed and modified with development in science. The most possible reason for a theory to be changed is that new evidence of new research can contradict the previous facts.

Thus, Option-C is the correct answer.

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.