How is the production of mercury from burning coal an environmental hazard?
a. high concentrations of mercury in the air leads to global warming.
b. mercury in water systems is transformed through biological processes into a substance that is toxic to animals.
c. mercury combines with other coal emissions in the air to produce ozone.
d. all of the above

not d ):

What causes the force that pushes magma from the magma chamber through the pipe and vent of a volcano?

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.

Which statement describes how favorable traits in a population relate to natural selection? they are the only traits that ever exist in the population. they build in the population over time. they are rarely passed on to offspring. they are found only in a few individuals within the population.