Group IV of the Periodic Table of the Elements contains carbon (C), silicon (Si) and several heavy metals. Carbon, of course, is the building block of life as we know it. So is it possible that a planet exists in some other solar system where silicon substitutes for carbon? Several science fiction stories feature silicon-based life-forms--sentient crystals, gruesome golden grains of sand and even a creature whose spoor or scat was bricks of silica left behind. The novellas are good reading, but there are a few problems with the chemistry.
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CRYSTALLINE CREATURES? Silicon can grow into a number of lifelike structures, but its chemistry makes it unlikely that it could be the basis for alien life-forms.</span>
Indeed, carbon and silicon share many characteristics. Each has a so-called valence of four--meaning that individual atoms make four bonds with other elements in forming chemical compounds. Each element bonds to oxygen. Each forms long chains, called polymers, in which it alternates with oxygen. In the simplest case, carbon yields a polymer called poly-acetal, a plastic used in synthetic fibers and equipment. Silicon yields polymeric silicones, which we use to waterproof cloth or lubricate metal and plastic parts.
A. Certain factors are dominant, and others are recessive
Answer:
B. Energy needs
Explanation:
As an individual ages there is a characteristic natural loss of muscle mass that occurs and increases as they move into older years. Changes in lifestyle, such as transition from employment to retirement, also account for a decrease in energy needs. This is because there is less amount of work done during retirement than when an individual is actively working.
The less amount of work is the reason why there is also a corresponding decrease in the energy needs.
They typically calculate approximate due dates based on the date of the last menstrual cycle.
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