Question 3
Original passage
Vatna jökull, 3,200 frozen square miles overlying Iceland's most active volcanic region, sits, as does the rest of the island, above a mantle plu mea column of hot rock that rises from the depths of Earth and feeds volcanoes with lava. Although it is paradoxical that Iceland's hottest region boasts its biggest ice cap, it is no coincidence: the ice sheet is huge and permanent precisely because lava flowing from the mantle plume has built the mountains so high. . . . During an eruption of any of the island's ice-covered volcanoes, up wel ling lava meets hundreds of feet of ice, producing trillions of gallons of melt water and confronting Icelanders with a three-pronged pestilence of fire, flood, and ice.
From Robert S. White, "The Ice Above, the Fire Below," Natural History June 2002: 43.
SUMMARY: The entire island of Iceland sits above a mantle plumea shaft of hot rock rising from the Earth's depths and feeding lava to volcanoes. According to Robert S. White, it is the lava flowing from the mantle plume that has made the mountains so high (43).
Question 3 options:

effective

ineffective