Once oxygen started to be manufactured by cyanobacteria, why did it take so long to build up to significant levels?
A) initially most of the oxygen escaped into space
B) oxidation of surface rock and ocean minerals occurred
C) initially most of the oxygen produced dissolved in the oceans
D) initially most of the oxygen was converted into water by reaction with hydrogen
B
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Series/Parallel Circuits: In the circuit shown in the figure, the resistor R has a variable resistance. As R is decreased, what happens to the currents?
A. I1 remains unchanged and I2 increases. B. I1 decreases and I2 decreases. C. I1 decreases and I2 increases. D. I1 increases and I2 decreases. E. I1 increases and I2 increases.
Compared to the central regions of spiral galaxies, we expect elliptical galaxies to have
A) higher mass-to-light ratios because stars in elliptical galaxies are dimmer than those in spirals. B) lower mass-to-light ratios because stars in elliptical galaxies are dimmer than those in spirals. C) higher mass-to-light ratios because stars in elliptical galaxies do not have high orbital velocities. D) lower mass-to-light ratios because elliptical galaxies have less gas and dust than spirals. E) the same mass-to-light ratio because they are made of the same material, stars and dark matter.
The Manicouagan reservoir near Quebec is an example of
A) a volcanic event. B) Earth's interaction with a comet's dust tail. C) cometary debris. D) a micrometeorite impact. E) a large meteorite impact.
Adding heat boosts free energy. The greater the free energy of reactants, the closer they are to ____
a. feedback inhibition b. an endergonic reaction c. an induced fit with an enzyme d. activation energy e. cofactor interaction