Answer:
1. A strong wind blows across a Midwestern prairie.
Explanation:
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.
