请问undersecretary of the Air Force是什么职位?

请问undersecretary of the Air Force是什么职位? undersecretary,vice minister和deputy secretary的区别?各用在什么场合,比如正式与非正式 请问 doubt of success 请问：Of course 请问get rid of 请问dawn of 请问：Of course 请问of course是什么意思? 请问use of the 请问each of 请问tens of thousands of tourists是什么意思? 请问lack of representativeness of convenience sampling. 请问The calling of the 请问be out of favor 请问boll of some sort 请问：charm sb out of 请问”nature of duties”是什么意思 请问order of the day