Which of the following best summarizes a claim made in this passage?
A Creating a sunshade in the stratosphere out of reflective particles could actually cool the Earth.
B How to launch sulfate particles in the stratosphere is a problem that hasn’t been solved yet.
C Geoengineers can design particles that would reduce the amount of sulfate placed in the stratosphere by erupting volcanoes.
D The sulfate scheme is the cheapest possible solution to global warming because it is a one-time solution.
Which sentence or phrase from the passage provides the best supporting evidence for the claim you identified in Part A?
A “Planes, balloons, battleship guns pointed upward—there is no shortage of possible delivery vehicles.”
B “After Mount Pinatubo erupted in 1991, launching ten million tons of sulfur into the stratosphere and spreading a sun-dimming haze around the planet, the average temperature dropped about a degree Fahrenheit for a year.”
C “With carefully designed particles, geoengineers might make do with a fraction of that tonnage—though because they fall out of the stratosphere, the particles would have to be delivered continually, year after year.”
D “Still, says Caldeira, the sulfate scheme would be ‘essentially free compared with the other costs of mitigating climate change.’”
