What can you infer is the reason fruit flies are the most commonly used organism for this type of investigation

In the case of genetic investigation, scientists used fruit flies as their model organism since they share 75% of the genes that cause disease with humans.  Fruit flies are also great to work in a research setting because they are relatively easy to take care of, especially compared to larger and more expensive organisms like rats or fish.

Explanation:

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i think it would be b. tissue because an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.

it would lead to upper respiratory infections and pneumonia.