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Câu hỏi :

Set in the red desert of central Australia is the mining town of Coober Pedy. At first sight, the town looks similar to many other such communities, but Coober Pedy is different. Sixty per cent of its population of 4,000 people lives underground. There are today about 800 underground houses as well as shops, hotels and even churches in the town and the surrounding hills. Once a site has been chosen, special tunneling machines are (30) ________ in to ceate passage and rooms in the sandstone. Rock pillars are left to support the roof, and door and windows are cut into the front. Houses are of all shapes and (31) ________, the largest having twenty rooms, and some even have their own swimming poll.