Alternative energy sources are those that do not deplete natural resources and do not harm the environment.
Options A, B, and C are all fossil fuels, which we know can be depleted and harm the environment.
The only valid option here is D, Geothermal energy.
Geothermal energy is both renewable and environmentally friendly.
Answer:
objective lenses
Explanation:
objective lenses with different magnifications, screwed into a circular "nosepiece" which may be rotated to select the required lens.
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