Printing was developed __________ the Song dynasty in China and it __________ Asian and European countries later on.
A:in; was spread to
B:in; spread to
C:on; was spread
D:on; spread
在以下四个选项中,有一个是不同类的,请把它找出来( )
用已调好的托盘天平测量物体的质量时,应将砝码放在天平的 ____盘.当放入20g、10g和5g的砝码各一个,游码拨到如图所示的位置时,指针恰好指在分度盘的中线处,则被测物体的质量为 ____ g.
下列计算正确的是( )
计算:① −22+30−(−12)−1
②a2·a4+(a2)3