<span>Physical activity and exercise typically lead to higher energy levels. As your body gets used to working hard consistently, you tend to be more prepared and in better physical condition. Your body begins to learn that you should burn up calories quickly to prepare to be active, and this results in increased energy levels even when you're not currently exercising.</span>
Hello, to answer your question. It is because all machines require a fuel or source to power it making it imperfect for using some source that may not be renewable.
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There are a couple of ways in which you can express the concentration of a solution, and here they are: gram per liter (g/L), molarity (M), parts per million (ppm.), and percents (%).
As you can see, only M appears in your answers, which means that the correct option should be (2) 3.5 M.