Energy is the ability to do work. The form of energy that living things need for these processes is chemical energy, and it comes from food. Autotrophs make their own food. Heterotrophs obtain food by eating other organisms. Organisms mainly use the molecules glucose and ATP for energy.
Explanation:i hope this is correct
A. Immune system
It helps our bodies fight everything that comes in our path.
The right answer is <span>Refractory period.
At the moment when the action potential is emitted, the fiber being depolarized, it is impossible to depolarize it again. It is, therefore, necessary to wait until the membrane potential returns to a value below the critical threshold in order to be able to excite it again. We are thus led to distinguish two periods that characterize its excitability.
An absolute refractory period: during which any stimulation, even supraliminal, is ineffective since the fiber is already depolarized.
A relative refractory period: during which a second action potential can be omitted provided that the depolarization produced by the excitation reaches the critical threshold, which implies that it is more important since the value of the resting potential has not been restored yet.</span>
Answer: Photosynthesis is the process of when a plant makes it's own food, and the main goal is to convert solar energy to chemical energy.
Explanation: Plants use photosynthesis by taking the sunlight, to synthesize foods from carbon dioxide and water. Since plants can't move and consume other organisms, they use photosynthesis. The formula is: 
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Like I said, the main goal is converting solar energy to chemical energy then store the chemical energy for future use, for example it can be used for Chemical batteries, Natural gas, Heat, Food, etc.
