— Is this book yours?—No, it's not ______. It's Betty's.
图A
图B
如图所示,平行板电容器与直流电源、理想二极管(正向电阻为零可以视为短路,反向电阻无穷大可以视为断路)连接,电源负极接地.初始电容器不带电,闭合开关稳定后,一带电油滴位于容器中的P点且处于静止状态.下列说法正确的是( )
“夫五千年以前,人户稀微,制作未备,何以能成此大工?”这是针对古代哪一建筑物而发出的疑问