Once photosynthesis evolved oxygen started to be released to Earth's atmosphere. why did it 1 point take a long time for oxygen to start to build up in the air?
A)because all the living organisms breathed it up
B)because the rain would wash it away
C)it was soaked up by ice
D)It was soaked up by the iron in rocks and iron in the ocean

Which of the following is the earliest era of earth's geologic time scale? cenozoic mesozoic precambrian paleozoic

Which of the following cognitive skills have not been displayed by animals? a. using tools b. forming concepts c. transmitting culture d. using syntax

Which of the following is true? a. under the current unemployment insurance system, benefits replace about 90 percent of the typical worker's prior pretax earnings. b. high benefit payments to unemployed workers will tend to increase the rate of unemployment. c. if a system of personal savings accounts replaced the current unemployment benefit system, the unemployment rate would fall to zero. d. the rate of unemployment in the large european economies has been persistently lower than that of the united states due to their more generous unemployment benefits.