Over the past 100 million years of Earth history, it is known that the magnetic poles have reversed themseves ______ times.
a - 0
b - 2
c - many
d - 25
c - many
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Given the following diagram, describe what happens electronically between these two molecules.
A. Hydrogens on oxygen W becomes slightly positively charged due to the oxygen molecule. B. Oxygen A becomes slightly positively charged due to the protons on the water molecule. C. Oxygen B becomes slightly positively charged due to the protons on the water molecule. D. Oxygen A becomes slightly negatively charged due to the oxygen molecule. E. none of the above
Which of the following combinations represents two cloud types that can produce precipitation?
A. cumulonimbus and stratocumulus B. nimbostratus and altostratus C. cumulonimbus and nimbostratus D. nimbostratus and cirrus
During alpha emission, the mass number is reduced by ________ and the atomic number is decreased by ________
A) 2; 4 B) 4; 2 C) 3; 6 D) 6; 4
Most of the countries experiencing food-security problems are in what region? (23 of the 28 countries are found here.)
A) Asia B) Middle East C) north Africa D) southeastern Europe E) sub-Saharan Africa