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

The diagram shows the positions of the sun, moon and earth during spring tides, when the high tides are at their highest and low tides at their lowest. what is it about these positions that causes these high and low tides?

Nwhat way does renewable energy differ from nonrenewable energy?

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)