When does a protostar become a true star?
A) when the star is 1 million years old
B) when the central temperature reaches 1 million Kelvin
C) when nuclear fusion begins in the core
D) when the thermal energy becomes trapped in the center
E) when the stellar winds and jets blow away the surrounding material

Project: analyze it! data collected over the past century shows the earth currently in a slight warming trend, with an increase over that period of a little more than 1.0°f in average global temperature. the question of what is causing the trend has sparked controversy in both scientific and political circles. some argue that while temperature fluctuations are a normal part of the earth's climate cycles historically, an increase in co2 produced by industrial pollution and other forms of human activity is contributing to and even accelerating the increase, potentially leading to significant environmental problems. others argue that pollution-caused co2 is not a factor and that the increase is caused by natural cycles alone.objectivesresearch credible positions for and against the existence of global warming. write a short essay briefly outlining each perspective. directions locate two well-researched, credible articles, one for and one against global warming. after reading the articles, write a 300-word essay addressing the following: what is global warming, as described in the articles? what arguments are given for and against the idea. what actions are recommended by each position? in your opinion, what can be learned from the debate? what would you like to do next?