—Ten years ago.
A:when you taught in this school
B:when did you teach in this school
C:how long you taught in this school
D:how long did you teach in this school
如图所示,将重2.2N的物块浸没在水中称量时,弹簧测力计的示数为1.2N,则物块受到的浮力为____ N,物块的体积为 ____ cm3(g=10N/kg)
60年前的万隆会议引起了世界的关注。下列对该会议的叙述,不正确的是( )
我国自主研发生产的一种碳纤维材料,各项性能均达到国际先进水平,其密度是钢的四分之一,下列关于碳纤维材料说法正确的是( )