Answer:
B
Explanation:
All living things need to breathe, even the microorganism which breathe by a process called diffusion. They might breathe using different of mechanisms or organs but THE POINT IS THEY NEED TO BREATHE.
Answer : Hydrogen.......:
The primary difficulty is the fact that we do not know all of the organisms that currently exist in the world along with those that existed in the past.
20 chromosomes because unfertilised eggs contains half the number of bodily chromosomes