The answer of the question is A
C upcoming would be the closest to future
I think the answer is frequency if I remember correctly
The reactants are like a key that fits into the enzyme forming the lock
The shorter the food chain, the larger amount of energy obtained.
Hence, the consumer furthest away from the producer obtains the least energy.
The quaternary consumer is furthest away. Most energy is lost by then. Hence, it has access to the smallest supply of energy.