（）是双极型全控电力电子器件。 ["P-MOSFET","TRIAC","GTR","GTO"]
生产中拉伸倍数如何确定？举例说明生产中如何实施？
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"]
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。
人体静息状态和剧烈运动状态的心脏输出量相差数倍。心输出量的增加量叫心力贮备。健康人通过锻炼可以加强心肌收缩力，从而发生以下哪些变化使心力贮备增加（） ["A.心舒期心室容积增加","B.心缩期心室容积减少","C.静息时心率低","D.运动时心率高"]
熔融纺丝冷却长度受哪些因素影响？
