Which biologist proposed elevating the three cell types to a level above kingdom, called domain?

Several billion years ago which gas was the least prevailant in the atmosphere

This is the interaction of two organisms where one is and the other is neither nor harmed.

Skulls of homo sapiens were found during an excavation. the skulls were preserved because the bodies were frozen. so, these fossils are ( 1 ) fossils. ( 1 ) a. mineralized b. mold c. original-tissue