Earth's oxygen is produced by the biological action of plants (photosynthesis) and without this, most of our oxygen would be locked up in the surface rocks.
(Earth's oxygen; is produced; by the biological action of plants (photosynthesis) and without this) (most of our oxygen; would be locked up; L:in the surface rocks)
Earth's oxygen most of our oxygen
is produced would be locked up
by the biological action of plants (photosynthesis) and without this
L:in the surface rocks