【单选题】It was not until he arrived at the railway station ______ he realized he had forgotten his ticket.
【单选题】Most Korean young people get plastic surgery______.
A.
during the winter vacation
B.
during the summer vacation
D.
before going on the job market
【判断题】我国目前要求空气检测必测项目有6项,分别是SO 2 、NO 2 、PM10、PM2.5、O 3 和CO 。
【单选题】等直杆上端固定,下端受集中力 F 作用,如图所示,杆件自重为 W =4 F 。以下结论错误的是
【单选题】下列哪一项关于维生素D的叙述与维生素的概念不符
【单选题】People work ______ the daytime and sleep ______ night. [ ]
【判断题】我国目前要求空气检测必测项目有6项,分别是SO2、NO2、PM10、PM2.5、O3和CO
【多选题】等直杆上端固定,下端受集中力 F 作用,如图所示,杆件自重为 W ,则杆内最大拉力为 [填空(1)] ,最大压力为 [填空(2)] 。(已知 W > F )