Which gas was not present around the time earth first formed?

methane
hydrogen
oxygen
nitrogen

Oxygen was not present around the time earth first formed. Hope this helps. :)

ecological efficiency: % of usable energy transferred as

biomass from one trophic level to the next typical is 10% efficient (90% of

energy is lost),is diagramed as the pyramid of energy flow. then osprey eagle

are tertiary consumer and the shrimp are primary consumer, so to balance

mass of shrimp (1/0.1) / 0.1 = 100 kg