A:mustn’t they
B:hadn’t they
C:haven’t they
D:didn’t they
如图甲所示是测电笔的结构,图乙和图丙中,正确使用测电笔的是图____,当用它插入插座的左孔时氖管不亮,插入右孔时氖管发光,则说明火线在插座的____孔.测电笔内部有一个大电阻,它的作用是____.
一战期间民族资本主义发展较快的行业不包括( )
It is ____ that the police have found the related evidence in solving the murder case. (报道的)