单项选择题

A. He has never lonely.
B. He is upset about business.
C. He started a business.
D. He upset his guests.
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单项选择题
A. A foreign language is very useful in getting a job with decent pay. B. We use a foreign language to communicate freely with a native speaker. C. It may be of help in negotiating a business contract with a foreign firm. D. We can travel around different countries in a less expensive way.
A. A foreign language is very useful in getting a job with decent pay.
B. We use a foreign language to communicate freely with a native speaker.
C. It may be of help in negotiating a business contract with a foreign firm.
D. We can travel around different countries in a less expensive way.
问答题
许多年前，科学家们就已经知道人们需要维生素D。维生素D帮助身体吸收钙质，从而促进骨骼和牙齿的生长并使其坚固。研究显示，缺乏维生素D会增大骨折的危险，而加量服用维生素D有助于防止骨折。健康专家们一直相信，每天短时间的日光照射能给人体提供足够的维生素D，因为人们的皮肤能把阳光转换成维生素D，并在身体里储存起来。
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