People in villages on the loess plateau in Luoyang have been living in caves since __________ times. Cave dwellings around a courtyard are a very interesting site. Having __________ a good place, the local people would dig a 100-sq-meter pit, dig some caves at __________, a tunnel leading to the ground at one side and a well in the center of the pit and __________ low walls at the four sides. The courtyard cave dwelling is warm in winter, cool in summer and rain and __________. The pits of different families are close to each other. When you are at the boundary line of the village, you will be __________ to hear cocks crow and dogs bark because you won't see any houses and people. If you come to Luoyang, remember to visit the cave dwelling in the countryside and enjoy a completely different world.