The correct answer is, Since 1860 two political parties, the Democrats and Republicans have dominated American politics.
Answer:
<h2>D. environmental cues elicit CRs that counteract the effect of the drug</h2>
Answer:
Burning of fossil fuels
Explanation:
Over the last 200 years, burning of fossil fuels has been the major source of carbon emission. Here, atmospheric concentrations of 12C, 13C, and 14C refers to the carbon isotopes (12C, 13C and 14C) and therefore the statement refers to carbon emissions. It is now no surprise that carbon concentrations in the atmosphere is responsible for the environmental changes and that fossil fuel burning is the reason behind increased atmospheric carbon concentrations as proven by scientific research.
