1. [单选题]If clearance between a piston and the cylinder wall is excessive, piston slap will occur. The slap itself is caused by_____.
A. alternation of side thrust
B. a breakdown of the lube oil film on the cylinder
C. worn piston boss piston pin bearings
D. fluctuating gas pressure in tile combustion space
2. [单选题]水面有油火，落水后的船员应：
A. 向横风方向潜泳
B. 向上风方向潜泳
C. 向下风方向潜泳
D. 都可以
3. [单选题]湿蒸汽的温度与该压力下的饱和温度之差等于( )。
A. 干度
B. 过热度
C. 零
D. 比潜热
