A. 陶行知创办的鼓楼幼稚同 B. 陶行知创办的燕子矶幼儿园 C. 陈鹤琴创办的鼓楼幼稚同 D. 陈鹤琴创办的燕子矶幼儿园
A. 正确 B. 错误
A variable pitch propeller B. A variable pitch nut C. A fixed pitch parallel D. A fixed pitch screw