A.) Electrons are Shared in a covalent bond.
The trachea is a tube that carries air inside the lungs.
Based on the law of conservation of energy, we know that we can't create energy, machines can only convert one type of energy into another. So, if we want to improve a machines's ability then we need to reduce it's loss energy (part of energy which is useless). Out of all the options only Option C fits best with it.
In short, Your Answer would be Option C
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Cochlea- <span>the part of the inner ear that contains the endings of the nerve that carries information about sound to the brain.</span>