7. where does oxygen come from in nature?

Most of Earth's oxygen comes from tiny ocean plants – called phytoplankton – that live near the water's surface and drift with the currents. So, mostly from plants, trees etc...

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Most of Earth's oxygen comes from tiny ocean plants called phytoplankton that live near the water's surface and drift with the currents.

Explanation:

answer; a male inherits only one allele of the x-linked gene controlling hair color;

answer; i believe that the correct answer is (lung);