Distress flares and smoke signals for small passenger vessels（）.
A. are not required aboard vessels on runs of less than 30 minutes duration
B. must be Coast Guard approved and stowed in a portable，watertight container
C. must be marked with an expiration date not more than 42 months from the date of manufacture
D. All of the above
Z12V190B型柴油机进气门（）与缸盖平面间距离为1.7-3mm。
A. 头底平面
B. 头上平面
C. 杆端部
D. 杆部中间
公司采用保守型流动资产投资策略时，流动资产的（）。
A. 短缺成本较高
B. 管理成本较低
C. 机会成本较低
D. 持有成本较高
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