The Great Oxygen Event marks the time, approximately 2.5 billion years ago, when ________
A) there was enough oxygen in the atmosphere to support a major burst of life on Earth
B) photosynthesis was clearly established and producing oxygen.
C) there was a massive volcanic eruption that lead to a very rapid increase in oxygen levels on Earth
D) there was significant oxygen in the atmosphere
E) there was a cataclysmic weather event that absorbed most of the oxygen in the atmosphere and locked it into iron deposits in the oceans
D
You might also like to view...
Recent U.S. legislation has mandated increased use of biofuels, and the number of ethanol refineries is growing rapidly. It is now predicted that by 2015, as much as ________% of the U.S. corn crop could go toward ethanol production.
A. 50% B. 70% C. 25% D. 100%
The success of De Anza College's sustainability program includes ________
A) requirement that faculty research include an environmental focus B) the expectation that all students take a specified number of environmental courses C) emphasis on using nonbiodegradable materials in offices and classrooms D) a supportive administration and increased environmental literacy of faculty E) requirements that students major in an environmental field
In addition to many different native languages, what are the main languages of Latin America?
A) English and German B) Flemish and Walloon C) French and Dutch D) Italian and Greek E) Spanish and Portuguese
Which statement best explains the US decision to get involved in the Vietnam War?
What will be an ideal response?