问题
选择题
钨是熔点最高的金属，广泛应用于拉制灯丝，有“光明使者”的美誉。我省蕴藏着丰富的钨矿资源冶炼金属钨常用到白钨矿石，其主要成分是钨酸钙(CaWO4)，钨酸钙中钨(W)的化合价为 [ ]
A．-6
B．+4
C．+6
D．+7
答案
答案：C
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钨是熔点最高的金属，广泛应用于拉制灯丝，有“光明使者”的美誉。我省蕴藏着丰富的钨矿资源冶炼金属钨常用到白钨矿石，其主要成分是钨酸钙(CaWO4)，钨酸钙中钨(W)的化合价为 [ ]
A．-6
B．+4
C．+6
D．+7
答案：C
The bullet (子弹头) train D106 from Changsha to Shanghai has a short stop in Quzhou for only one minute. Named 21 the letter D, the new trains run at speeds of 200 to 250 kilometers one hour. This is much 22 than Z-type and T-type trains. For example, it 23 take people 12 hours to travel from Shanghai to Beijing. But now it only 24 10. The most interesting part of the bullet trains is the revolving (旋转的) seats. People can adjust (调整) their seats as they like, so that it is 25 for you to talk with others around you face to face. The new trains run 26 big cities. They 27 the long trips much faster and more comfortable. However, many passengers still won’t choose the bullet trains 28 some reasons. The ticket 29 of the bullet trains are much higher. For example, a hard seat ticket from Beijing to Jinan is only 90 yuan for T-type trains. But on the bullet trains all the seats are 30 . And they cost 153 to 184 yuan. On the other hand, the bullet trains don’t stop at small stations.
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