Final answer:
The control of metabolic rates in animals is chiefly influenced by temperature,option a) is the answer, as it affects metabolic processes either by increasing demand for energy at higher temperatures or reducing it at lower temperatures.
Step-by-step explanation:
Metabolic rates in animals are primarily controlled by temperature. Temperature significantly influences the rate of chemical reactions within an organism, and thus affects its metabolism. Organisms must adapt to maintain a stable body temperature in varying environmental conditions, which can include behaviors such as hibernation, aestivation, and migration. For instance, when temperatures are too high or low, enzymes that catalyze metabolic processes can become denatured, leading to the necessity of maintaining a constant body temperature for proper functioning.
Moreover, temperature’s impact on growth is profound because a 10°C rise can double or triple an organism's metabolic rate. This increase in metabolic rate demands more food and energy. Alternately, lower temperatures reduce metabolic rates, lessening nutritional and oxygen requirements. It's important to recognize that while an answer in 200 words cannot encompass all variables affecting metabolic rates, such as moisture and relative humidity, temperature stands out as a key determinant.
In summary, the correct answer is primarily a. Temperature, as it poses the most direct influence on an organism's metabolic processes.