A、Construction materials could easily be found. B、There were no caves where they worked. C、They were tired of living in caves. D

Since the first prehistoric artist drew the first pictures on the walls of a cave, artists have been using stone, clay, paint, jewels, metals and hundreds of other materials to tell the story of the history of the world.
    Building, paintings and clothing styles can tell us what people thought and felt about their world.
    Cave paintings from the Old Stone Age show us animals and hunters. But more important, they also show us the weapons that were in use in prehistoric times. They show that fire was used, and that people had learned to make sewing needles from bone, and that stone tools had been invented for digging and cutting. Some roughly formed images have been found in the caves, too, showing that cave dwellers appreciated the beauty of the human form.
    In the New Stone Age, people learned to weave cloth. They didn’t have to depend on animals’ skins for clothing. They also learned to build houses, since the best farming land was far away from the mountain caves in which their forefathers had lived.