That white car is not ___________. It is ____________.
A:Jack's; my
B:Jack's; mine
C:Jack; mine
D:Jack; my
已知i是虚数单位,若复数(2+i)(1+ai)是纯虚数,则实数a等于 ( )
以下对科学探究的基本过程的叙述正确的是( )