48. Geologists are working hard to better understand why volcanoes erupt, so they can warn peoplein advance.
(A) Earthquakes often precede an eruption.
(B) In addition, many eruptions areaccompanied by heavy rains.
(C) However, because the quakes may come months before theblast, or only hours before, they cannot be used for precise forecasts.
(D) This is why it is hardfor researchers to predict when a volcano like Mt. St. Lorenzo will erupt again in the future.