Easy. Answer is oxygen because it says which one was missing before any life was on earth. And in order to have life on earth you need oxygen!
:)
The answer should be NEURONES (nerve cells).
Neurons transmit electrical signals called NERVE IMPULSES from the cell body through the axon to the end plate. The junction between the end plate and the adjacent cell is called SYNAPSE. impulses passes through the synapse by diffusion of chemicals.
The<span> duodenum is the first segment of the small intestine</span>
The best answer is C
Hope it helped!! :)
The correct answer is C. humans
Language is an advanced system for communication available only to humans. Dolphins, chimps, and bees, use other means to communicate, but it is not a language, it's mostly things like smells or pheromones or similar things.