In a food web, an organism takes in carbon dioxide from its environment to fuel its life processes. What is one way the organism returns oxygen to the environment?
O breathing in air
O photosynthesis
O cellular respiration
O releasing heat energy

your answer is rna to the question.

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

hope this

for a different answer set the answer would be because the oxygen in the water had depleted (apex)