I believe the answer is a.
Both Radioactive dating of rocks retrieved from the world and Comparing cratering rates on one world to those on another.
Geologists can find the relative age of impact craters on a world because
the ones on top must be younger.
Scientists know the history of Earth's magnetic field because the magnetic field gets frozen into rocks, and plate tectonics spreads them out.
Hope it helps
The quote states that we should be using solar energy before our limited amount of naturally occurring oil and coal runs out. Meaning; we should be proactively working towards solar power rather than to wait for our resource to run out to start.
The value of goods and services produced within a country in a year<span>
hope this helps
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