TOEFL Listening: ETS-TOEFL听力机经 - 98414K7D5S53GOC6P$

What point does the professor emphasize when he discusses Mount ST Helens? A. Magma begins entering the magma chamber hours before an eruption. B. Ice and snow typically melt on only one side of a volcano before it erupts. C. A bulge on a volcano can grow dramatically in a relatively short period of time. D. Bulges on volcanoes may develop steam vents.