中继阀在制动位时,下面各部件的工作情况正确的应是:() ["A、供风阀打开而排风阀关闭","B、供风阀关闭而排风阀打开","C、供风阀与排风阀均关闭","D、供风阀与排风阀均打开"]
与其它遗传标记相比,分子标记的优点?
在精馏塔单元中灵敏塔板温度降至()以下时关塔顶冷凝器冷凝水,手动关闭PV102A ["50%","40%","52%","51%"]
列车管常用制动排风时,紧急阀95中的紧急鞲鞴的工作位置是:() ["A、与阀顶盖接触","B、悬在中间","C、与放风(夹心)阀接触","D、下部"]
分配阀在紧急制动位时,主阀部膜板鞲鞴杆与滑阀的间隙应在滑阀的:() ["A、上部","B、中部","C、下部","D、内部"]
简述胚状体与器官发生型的区别。