用20分度的游标卡尺测量一个物体的长度,得到图1所示,读数为____ cm.
用螺旋测微器测量金属丝的直径,从图2中读出金属丝的直径为____ mm.
已知X、Y、Z三种金属能发生下列反应:()X + H2SO4 = XSO4 + H2↑ Y + Z(NO3)2 = Y(NO3)2 + Z Z + X(NO3)2 =Z(NO3)2 + X则X、Y、Z三种金属与氢的活动性由强到弱的顺序为( )
-Can you ______me the answer_____ this question?
-Sorry. It’s too difficult.
( )This is the hall in my school.We can sing,dance and act a short play in it.
孟子提出“民为贵,社稷次之,君为轻”,黄宗羲主张“天下为主,君为客”。从中可以看出( )