C. cell wall. This discovery was made by Robert Hooke upon studying the honeycomb like structure of cork and compared it to the dead appearance of the cell wall.
The answer is D. Food Threshold is the amount of food capable on feeding the organisms.
Small herbivorous fish would occupy the role of a C. primary consumer. Primary consumers consume primary producers, and primary consumers are then consumed by secondary consumers. Once secondary consumers die, they are consumed oftentimes by decomposers.
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