【判断题】一平面力系向 A 、 B 两点简化,结果相同,则主矢、主矩都不为零。
【单选题】According to the passage, which of the following statements is NOT true?
A.
It is not quite easy to tell how " rock and roll" began.
B.
Both the blues and country music were developed by the musicians in the southern United States.
C.
Both the Europeans and the African slaves came to America during the 17th century.
D.
It was the blues songs recorded in Memphis that made Elvis Presley popular throughout the nation.
【单选题】对生产经营单位安全生产管理人员的能力要求,《安全生产法》规定,生产经营单位的主要负责人和安全生产管理人员必须具备与本单位所从事的生产经营活动相适应的( )。
【单选题】并励电动机,PN = 37kW,UN = 440V,IaN = 97A,Ra = 0.332Ω,pf = 1496 W,则p0应为[ ]。
【单选题】There is only one ticket. Either you or Mary ______ going to the cinema tomorrow.