A:where
B:which
C:in which
D:what
一架飞机每分飞行21千米,每时飞行()千米。
— Has your brother completed this design?
— Not yet. He ____ (work) on it last night .
日本人在重庆拿到了清政府准许其开办工厂的营业执照,这一现象最早可能出现 ( )