（）refers to the angle between true North and the heading line of the ship.
A. True position
B. True meridian
C. True course
D. True bearing
能源结算页面中显示已合计时间的先决条件？（）
A. 能源
B. 开始时间
C. 结束时间
D. 核算单元名称
Wristpin bearings are difficult to lubricate because of their oscillating motion and（）
A. their free-floating design
B. their relatively small size
C. the reciprocating motion of the piston
D. their position in the lubrication system
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