阅读以下资料，回答下面问题。
20世纪70年代，在世界新发现的大油田中，海上油田有31个，约占51.7%。在新增加的地质储量中，海洋占42%。海上钻井平台总数为7021座，其中美国有1079座，委内瑞拉有5033座，苏联有840座。1977年，近海油田有500个，产量4.6亿吨，占世界总产量的15.6%。
70年代美国海上钻井平台数约占世界总数的比例是( )。
A．42%
B．15%
C．72%
D．10%
参考答案：B
解析：美国海上钻井平台有1079座，世界共有钻井7021座，[*]。故选B。
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| Sheepdogs are very important to farmers. Sheepdogs help farmers to find their 1 and bring them back to the farm. Mike, a farmer from a 2 , has a very clever and honest sheepdog 3 Bobby. He has built a little but 4 house for Bobby and he regards the dog 5 a family member. He often says. "Bobby is the best dog in the world. He works hard and 6 my sheep very well." If the dog house is 7 . Mike knows Bobby must be with his sheep. Mike 8 with Bobby through whistles (口哨). Bobby can understand many different instructions from those 9 . And Bobby can also 10 himself by barking (狗叫) or doing other actions. Mike loves Bobby very much. They are getting on well with each other. | ||||
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