单项选择题

A．Crowded air traffic.
B．The large size of airplanes.
C．Mistakes by air traffic controllers.
D．Bad weather.
<上一题 目录 下一题>
热门 试题

填空题
issued
单项选择题
A．There are not accepted standards.B．There are too many schools.C．Decentralization brings much diversity.D．No one has critically studied the subject.
A．There are not accepted standards.
B．There are too many schools.
C．Decentralization brings much diversity.
D．No one has critically studied the subject.
相关试题