()是指经济正常情况下的失业量与劳动力总人数的比率。
A.正常失业率
B.标准失业率
C.自然失业率
D.调整性失业率
参考答案:C
Which of the following statements is NOT tree of "free flight" a. Commercial aircraft is guided by GPS. b. Civilian aircraft are free to move over all territories. c. Cargo carriers no longer collide with one another. d. Passenger flights are safe to fly with military aircrafts.
硅稳压管加正向电压超过()电压时导通。