Most mountains are very old. They were here before there were people. But some mountains are still being made. Theyare volcanoes.         Mexico has a new mountain. It began in 1943 near the town of Paricutin. The mountain grew in a field. The groundbegan to shake. Part of the ground opened. Smoke and hot rocks came out of the opening. The hot rocks began to pile up intoa big hill. The hill was shaped like a cone.         Out of the cone came hot melted rock. This melted rock was lava. It moved like a river. It ran down the sides of the cone.It covered more and more of the land. Soon it covered the town of Paricutin. In the open air, the lava became cold and hard. At last, in 1952, lava stopped coming from the volcano. Mexico had a new, small mountain.  ※ Mexico 墨西哥 field 田野 pile 堆起 cone 圓錐體 melt 熔化 cover 覆蓋
【題組】18. The word in the story that means hot, melted rock is _________ .
(A) volcano
(B) mountain
(C) lava
(D) guava