A:had come, had writte
B:came, wrote
C:come, have writte
D:came, had writte
多音字组词
和hé____ huó____
下列各点中,符合“西半球、北半球、低纬度”三个条件的是( )
如图所示,用一张硬卡片先后快拨和慢拨木梳的齿,听到卡片声音发生变化.这个实验用来探究( )