Enzymes are biological catalysts which speed up the speed of reaction by lowering the activation energy without itself being consumed for e.g to digest proteins there are dfrn enzymes and to digest carbohydrates there are dfrn enzymes every enzyme is specific in its function
A catalyst lowers activation energy. Choice C is your answer.
A geologist studies all of those.
This is still a reliable source because it clearly cites scientific research. Sometimes sources flatly contradict a given statement, study or an existing fact. In that case, there are things that we need to consider like the source of the evidence, is there outside evidence that supports one of the sources, and how do the conflicting sources fit with other existing facts present about the topic.