What’s the greenhouse effect? A. The release of extra moisture from water vapor
B. The trapping of warm air in cities
C. Human-caused global warming
D. The regulation of atmospheric and surface temperatures

Geologists know that potassium-40 decays to argon-40, with a half-life of 1.3 billion years. if an analysis of a feldspar crystal in a sample of granite shows that 75 percent of the potassium-40 atoms have decayed to form argon-40, what is the age of the granite

Read the article titled "trans-saharan migration routes to north africa and the eu: historical roots and current trends." why do tens of thousands of sub-saharan africans try to cross the mediterranean each year? how are these refugees commonly portrayed? (site 1)

Where was oil production at its highest in the 1980s and still remains important to the russian economy? central asia the ural mountains russian siberia the caucasus region