建筑防火设计以（）为目标。 A．防止火灾危害  B．减少火灾危害  C．保护人身安全

如图所示，电流表示数为2.5A，电压表示数为6V．若将R₁和R₂串联在同一电源上时，通过R₁的电流为0.6A，求R₁和R₂的值．（已知R₁＞R₂）

We're going to ______________ Kunming this summer holiday. [ ]

A. visited

B. visits

C. visit

I _____ my homework while my parents _____ TV last night. [ ]

A. did; have watched

B. was doing; were watching

C. had done; were watching

D. would do; were watching

下列不符合三度房室传导阻滞心电图表现的是（）

A.P波规则出现

B.QRS波群规则出现

C.PR间期不固定

D.心室律快于心房律

E.出现交界性或室性逸搏心律

中秋节来历是什么？