如图所示,a和b是从A点以相同的动能射入匀强磁场的两个带等量电荷的粒子运动的半圆形径迹,已知其半径ra=2rb,则由此可知( )
A:两粒子均带正电,质量比ma:mb=1:4
B:两粒子均带负电,质量比ma:mb=1:4
C:两粒子均带正电,质量比ma:mb=4:1
D:两粒子均带负电,质量比ma:mb=4:1
— lives. We hope there won't be wars any more.
下列词语中,加下划线字的注音全都正确的一项是( )
—Would you like some noodles?
—Yes, please.