Thedesertsoftheworldarenotallcoveredwithsand.Manyofthem...
问题详情：Thedesertsoftheworldarenotallcoveredwithsand.Manyofthemhavesurfacesofrockorclayorsmallstones.Theyarenotflat,either.Theyoftenhavehighhillsanddeepvalleys.Thereissomeplants’lifeinmanypartsofthed...