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Which of the following is not am example of a polymer? protein nylon kevlar concreta

Which best describes how fluids change as they travel through different portions of the convection currents? they change to solids at the outer portion of the convection currents. they change to solids at the inner portion of the convection currents. they become more dense at the outer portion of the convection currents. they become more dense at the inner portion of the convection currents

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration