题干

最新科技成果“泡沫铝”是轻质多孔泡沫铝合金的简称,它除了具有隔音、隔热等优良性能外,同时还具有金属铝固有的防潮、耐蚀等性能.你认为该材料具有耐腐蚀性质的原因是(  )


A:铝的金属活动性比较差

B:金属铝易与氧气发生反应产生致密的氧化膜

C:泡沫铝的多孔结构

D:铝的表面有泡沫成分使铝与外界隔绝

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答案(点此获取答案解析)

B

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    I travel a lot, and I find out different “styles” of directions every time I ask “How can I get to the post office?”

    Foreign tourists are often confused in Japan because most streets there don't have names; in Japan, people use landmarks(地标)in their directions instead of street names. For example, the Japanese will say to travelers, “Go straight down to the corner. Turn left at the big hotel and go past a fruit market. The post office is across from the bus stop.”

    In the countryside of the American Midwest, there are not usually many landmarks. There are no mountains, so the land is very flat; in many places there are no towns or buildings within miles. Instead of landmarks, people will tell you directions and distances. In Kansas or Iowa, for example, people will say, “Go north two miles. Turn east, and then go another mile.”

    People in Los Angeles, California, have no idea of distance on the map; they measure distance in time, not miles. “How far away is the post office?” you ask. “Oh,” they answer, “it's about five minutes from here.” You say, “Yes, but how many miles away is it?” They don't know.

    It's true that a person doesn't know the answer to your question sometimes. What happens in such a situation? A New Yorker might say, “Sorry, I have no idea.” But in Yucatan, Mexico, no one answers “I don't know.” People in Yucatan believe that “I don't know” is impolite. They usually give an answer, often a wrong one. A tourist can get very, very lost in Yucatan!