The correct option is C.
The recovery process is used to remove refrigerant from an AC system in order to store it in an external container. The refrigerant has to be removed because it destroys ozone layer and cause global warming. It also has negative effects on the living organisms generally.<span />
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The lungs expand and with that you breathe in air as the diaphram contracts and relaxs to cause "breathing"
The most likely explanation for the variation is the offspring were produced from different combination of genes. A single pair of gold fish mentioned in the question means a male and a female gold fish. The two of them mated and contributed different genes to the fertilized fish eggs, this results in production of various body shape and colouration which is known as variation.
