In an internal combustion engine, which of the devices listed will force the compression rings to seal the compression gases in the space above the piston?（） ["Used of bimetallic piston rings","Ring gap pre-tensioning","Thermal increase in ring-end clearance","Gas pressure acting against the back of the ring"]
简述军用小艇的特点。
熔融纺丝冷却长度受哪些因素影响？
消费（）性要求市场上提供的商品品种繁多，花色丰富，规格齐全。 ["层次","相关","多样","发展"]
公关传播管理与一般管理的区别是什么？
2000年发布实施的《国家行政机关公文处理办法》规定的对外发文的文种有（）种。
