Which best describes the total mass of substances before and after a combustion reaction?
A. The mass is the same because atoms are not created or
destroyed.
B. The mass is greater after the reaction because the number of
atoms increases.
C. The mass is the same because the molecules do not change.
D. The mass is less after the reaction because gases are produced.

B. The mass is greater after the reaction because the number of

atoms increases.

The atmospheric carbon dioxide concentration has risen from about 270 parts per million (ppm) before 1700 to about 355 ppm today. Climate changes, including a mean global surface temperature rise of between 2.8 and 5.2°C, have been predicted by five independent general circulation models (GCMs) for a doubling of the carbon dioxide concentration. The objectives of this paper are to examine plant responses to rising carbon dioxide levels and climatic changes and to interpret the consequences of these changes on crop water use and water resources for the United States.

Explanation:

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