I believe it is B but I’m not 100% sure
<span>The elements that are found in a high proportion in Earth's crust are oxygen, aluminium, iron, calcium, potassium, sodium, and magnesium. But for your Option, I think it is B) Oxygen and Silicon. This is because Oxygen makes 46.6% while Silicon makes 27.7% of the Earth crust.</span>
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Well, I think the answer would be, Both biomass and coal energies are inexpensive, but they release greenhouse gases.</span>