047.
Nowadays in the United States, more and more people are beginning to build underground houses which save open land. When houses are underground, there is more land for parks, playgrounds and gardens. Underground houses also save energy. They use only a little energy to stay warm or cool.
As we know, the idea of underground houses is very old. People in the past lived in underground hosues and underground cities in China. And today you can find large underground shopping centers in China, Japan, South Korea and Canada as well. Some countries also build underground factories and shop-houses to hold things.
Joyce Rinker has an underground house in Michigan. One day in February, the outside temperature was a cold -22℃, but the temperature inside his house was a warm 16℃. The next year, in July, the outside temperature was a hot 42℃, but the temperature inside was a comfortable 22℃.

答案解析：
(1) 正确答案为C。根据build underground houses which save open land建造地下房屋可以节省空地，以及Underground houses also save energy.地下房屋也节省能源。可知，人们建造地下房屋的原因是节省土地和能源，因此C项正确。
(2) 正确答案为C。根据People in the past lived in underground hosues and underground cities in China.过去，中国民众生活在地下房屋和地下城市中。可知，使用了很长时间地下房屋的是中国，因此C项正确。
(3) 正确答案为B。根据the outside temperature was a cold -22℃, but the temperature inside his house was a warm 16℃. 外面的温度已经是零下22度了，而他屋里的温度是温暖的16度。因此可知外面零下22度时，他屋里是16度，因此B项正确。