多缸发动机各缸的次级点火电压同时显示于屏幕,即为()。 ["A、直列波","B、重叠波","C、高压波"]
一些草花根部不死,次年再萌芽生长的花卉为()花卉。 ["二年生","宿根","球根"]
脊髓灰质炎的传播途径() ["血液传播","虫媒传播","粪-口途径","空气飞沫传播","经土壤传播"]
脊髓灰质炎的主要传染源是() ["无症状病毒携带者","猴","病人","隐性感染者","猩猩"]
进气管真空度常用()检测最为方便快捷 ["A、示波器","B、发动机综合性能分析仪","C、真空表"]
变压器绕组导线焊接有哪些要求?