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The answer is B. Hydrogen Bonds
I think that that the answer should be C asexual reproduction of a single-celled organism
The major causes of the greenhouse effect is excessive carbon dioxide gas in the atmosphere. The greenhouse effect is a process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by green house gases, such as carbon dioxide, water vapor, metahne, nitrous oxide, and ozone. The absorbed energy warms the atmosphere and the surface of the Earth.