生活在中国黄河中上游的黄土高原(the loess Plateau)上的人们，利用哪里的黄土层建造了一种独特的住宅—窑洞(cave-dwelling)。窑洞分为土窑、石窑、砖窑等几种。土窑是靠着山坡挖掘成的黄土窑洞，这种窑洞冬暖夏凉，保温和隔音效果最好。石窑和砖窑是先用石块或者砖砌成拱形洞，然后在上面盖上厚厚的黄土，即坚固又美观。由于建造窑洞不需要钢材和水泥，所以窑洞的造价较低。随着社会的发展，人们对窑洞的建造不断改进，黄土高原上冬暖夏凉的窑洞越来越舒适美观了。

【参考译文】

People living in the Loess Plateau which lies in the middle and upper reaches of the Yellow River make use of the solid to build unique residences called cave-dwellings. These can be further divided into earthen, rock-walled and brick-walled types. Earthen cave-dwellings are hollowed out of mountain slopes; they are warm in winter and cool in summer, and are also sound-proof. Stones or brick-walled carve-dwellings are usually built with stones or bricks first into arch-shaped house and then covered with a thick layer of earth. Since there is no need for steel and cement, the building cost is low. As society progresses, construction of cave-dwelling keeps improving, and today, such houses are more comfortable inside and more pleasant in appearance.