1 the atmosphere because gas is everywhere.
It would be uracil (C)
thymine would be complementary to adenine in DNA but because it is RNA it is replaced by uracil.
Here is what all 3 symbiotic relationships are: Parasitism is where one organism is benefited and the other is harmed. Commensalism one organism is benefited and the other one is not helped or harmed. Mutualism is were both organisms are benefited or both help each other. Easy ways to remember symbiotic relationships :)
