为方便记忆,某同学画了下面这张学习示意图。该示意图反映的制度是( )
A:郡县制
B:分封制
C:王位世袭制
D:禅让制
— How much is the ____?
— ____ yuan.
My sister likes singing, but she can't sing _____.
一颗图钉尖的面积是5×10-4cm2,图钉帽的面积是0.5×10-4m2,手指对图钉的压力为20N,则图钉尖对墙面产生的压强是____Pa ,在1标准大气压下图钉帽受到大气的压力是____N (1标准大气压为P0=1.0× 105Pa )