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【单选题】
In modern society, ( ), as the primary source of energy, would affect the national security.
A.
coal
B.
nuclear energy
C.
fossil fuels
D.
petroleum
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参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【多选题】What are energy security issues in Middle East?
A.
Iran’s nuclear threat
B.
Iran ongoing conflict with the USA
C.
Terror threat of radicals in Saudi Arabia
D.
Gaza strip issues
E.
Wars in Iraq and Afghanistan
F.
Tension between Pakistan and India over Kashmir
【单选题】滚珠丝杠螺母副消除间隙的方法常采用双螺母结构,利用两个螺母的相对轴向位移,使两个滚珠螺母中的滚珠分别贴紧在螺旋滚道的两个相反的侧面上,预紧力要小于最大轴向载荷( )。
A.
1/2
B.
1/3
C.
1/4
【单选题】what is the third profit source?
A.
technology
B.
raw materials
C.
logistics
D.
labor