Read the text, then answer the questions.

glaciers are slow‑moving masses of snow and ice. they form over thousands of years in areas where more snow accumulates than melts. glaciers can be the size of a football field or much larger, like the size of a town. however, even though glaciers are very large, they do not stand still. rather, the weight of the ice causes them to slowly move. they can retreat in warmer years and advance in years with more snowfall. the slow movement of glaciers down mountains creates different landforms, such as glacial valleys. glaciers cover ten percent of earth’s surface and hold 75 percent of its fresh water. they can be found on every continent except australia.

what is the author’s purpose in writing the text?
a. to teach the reader about a special type of glacier
b. to warn the reader that glaciers are advancing
c. to inform the reader about characteristics of glaciers
d. to persuade the reader that glaciers should be protected