Answer:
Option (D)
Explanation:
In terms of chemistry, a catalyst is usually defined as the substance that is commonly used in a reaction in order to increase the rate of reaction, without getting consumed. It helps in the reduction of activation energy.
In the given case, the lever or a person can be considered as a catalyst because both of these will increase the efficiency (or rate) in removing the rock from the top of the perch. Thus, the lever or the human will remain the same after the removal of rock as a catalyst can be recovered after the reaction.
Therefore, the correct answer is option (D).
A disturbance would be things like lava, flows, newly formed sand dunes, or rocks left from a retreating glacier. These are disturbances because Primary Successions happen in lifeless areas, which soil is incapable of sustaining life.
Systemic circulation is the circulation of blood through<span> the arteries, capillaries, and veins of the general system.
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