Select the correct text in the passage.
Which sentence best refines the central idea of the passage?

(10) One critical factor in future rates of snow and ice melt is the role of dust, soot and pollution that settle on the frozen surfaces. Pristine white snow reflects more than 90% of incoming solar radiation back into the atmosphere. But when snow is blanketed by darker-colored particles of soot or dust, this coating absorbs more heat and the snow melts faster. Research has shown that the reason the Little Ice Age ended in Europe was the coating of soot deposited on the Alps by the Industrial Revolution. In Asia, the last 35 years have seen significant increases in the amount of soot settling on mountain snow.Whether these Asian ranges will react the same way the Alps did centuries ago is an important question....