DBCAD
小题1:根据They painted pictures inside caves, and these are the rock paintings that have given us so much information about Aboriginal life.可知选D。
小题1:根据From this we know that the Aborigines started using boomerangs for hunting at that time.可知选B。
小题1:根据The Aborigines believed that spirits made people, animals and plants, and that these spirits still live in the earth.及下文描述可知选C。
小题1:根据Instead, things were decided by the older men in a group.可知选A。
小题1:根据短文最后一段描述可知战争和疾病是土著居民数量小的根本原因，故选D。