Which of the following statements concerning cylinder liner wear is true?()
A. Liner wear is distributed equally between the upper and lower portions of the cylinder
B. Excessive liner wear causes wear between piston ring and groove
C. Excessive, but uniform liner wear will not cause wear between piston ring and groove
D. Liner wear is normally greatest in the middle of the cylinder
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下哪项不属于全球社会面临的“灰色地带”的威胁()。
A. 恐怖主义
B. 人口增多
C. 环境恶化
D. 毒品走私
淋水盘式热力除氧器的回水及软水从除氧头()两侧引入,经配水盘和淋盘下淋。
A. 中部
B. 下部
C. 顶部
D. 中下部
接触悬挂上承力索中性区两端,各应装设一组()电连接器。
哈尔滨一号线最高试验速度为()km/h,最高运行速度为()km/h。