How is efficiency related to systems?

The efficiency indicates the manner in which the inputs are used by the system. Being efficient means the system uses inputs in a `right' way. If the input-output ratio is adverse, we say that the system is inefficient though it produces the desired output.

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cats appear to have glowing cat eyes because the back of their eyeballs includes a special reflective surface called the tapetum lucidum. this lets them see better during the night, giving them a much better vision.

the answer would be..

b. sucking