One of the most important sources of energy is the sun. The energy of the sun is the original source of most of the energy found on earth. We get solar heat energy from the sun, and sunlight can also be used to produce electricity from solar (photovoltaic) cells
1) Renewable energy
energy from a source that is not depleted when used, such as wind or solar power
2) non renewable energy
A non-renewable resource is a natural resource that cannot be readily replaced by natural means at a pace quick enough to keep up with consumption

Answer: Serotonin is likely in short supply
Explanation: serotonin is a neurotransmitter produced by nerve cells that is involved in depression, appetite, and is crucial in maintaining a sense of well-being, security, etc. It is called the happy chemical because of it involvement in making one happy. An imbalance influences the mood of an individual.
the variable is that it gets bleach longer it has less oxygen