A:My mother wrote a book last year.
B:My mother wrote a letter last Sunday.
如图所示,是用直尺和圆规作一个角等于已知角的示意图,则说明∠A′O′B′=∠AOB的依据是( )
精子和卵细胞相遇是在( )
“风声、雨声、读书声,声声入耳;家事、国事、天下事,事事关心.”是我们耳熟能详的对联,其中人耳能够区分“风声”、“雨声”、“读书声”是依据声音的( )来区分的.