Which sentence describes energy flow through a natural (not manufactured) system? 1. A strong wind blows across a Midwestern prairie. 2. The wind forces the blades of a wind turbine to rotate. 3. As the blades spin, the turbine converts mechanical energy to electrical energy. 4. The electricity generated by the wind turbine is used to power nearby homes.

As you may already know, wind is a source of energy. Keeping this in mind we can realize that among the options given in the above question, the only one that shows the flow of this energy through a natural system is the option.

Natural system is that which occurs naturally in nature without the intervention of man. With this we can say that the blades of a wind turbine is not a natural system because it was manufactured by man. Therefore, options 2,3 and 4 are not the correct answer to your question.

A prairie, on the other hand, is a natural system, which is not man-made and occurs naturally in nature. For this reason, we can say that the correct answer to your question is option 1.