Very simple. You can't renew it. Which one of the options seem like you cannot renew the resource in a reasonable amount of time?<span />
The Milky Way is a spiral galaxy
hope this helps:)
Inner core was found to be solid after observing the motion of P waves.
Explanation:
Seismologist Inge Lehmann, studied the seismic waves of an earthquake and discovered about inner core in the mantle layer of Earth. She States that there is a boundary of discontinuity between the outer and inner core of Earth.
She studied the travel of secondary and primary waves during an earthquake and how it flows at different shells of Earth's layer which helped her in finding about the inner core of mantle. She observed that the inner core is a solid layer inside the molten layer of outer core
Answer: Natural variation.
