— The classroom is ______ clean ______ it was yesterday.— Sorry, I forgot to clean it.
A:as; as
B:so; as
C:not as; as
D:more; than
读我国人口分布界线图,下列说法错误的是( )
某同学用如图所示装置做“研究电磁感应现象”实验.正确连接后,他先将变阻器的滑动片P置于a b的中点,在闭合电键瞬间,电流计的指针向右摆,说明____(选填“大线圈”或“小线圈”)有电流流过.闭合电键后,为使电流计的指针再向右摆,应将变阻器的滑动片P向____端滑(选填“a”或“b”).