The most important source of the free oxygen in our atmosphere is:
A) green plants that carry on photosynthesis.
B) the dissociation of water vapor in the upper atmosphere.
C) deforestation.
D) volcanic degassing.
Question 2
Students at MIT developed a method to produce ________ from agricultural wastes, resulting in a safer indoor fuel for use in developing countries.
A) ethanol B) biodiesel C) fuel cells D) wood E) charcoal
