Answer:
Habitat/Environment. Either can be right
Oceanic crust has been forming on Earth for over 4 billion years, all of the sea floor older than <span>about 200 million years. </span>
It carries deoxygenated blood from the right ventricle to the lungs
All living organisms are made of only 20 different aminoacids- this is the correct answer! This means that the genetic code only codes for those 20 aminoacids (for example Glutamine and Lysine).
The 20 aminoacids that can form proteins are also called Proteinogenic amino acids.