A:It was colder than today.
B:It was warmer than today.
C:It was as cold as today.
真空中两个静止点电荷间的相互作用力为F,若电量不变,间距变为原来的2倍,则两点电荷间的作用力大小变为( )
下列关于平静状态下呼吸过程的叙述,哪项是正确的( )