A:excuse me
B:I'm sorry
C:thank you
D:never mind
在研究电流跟电压、电阻的关系实验中,当研究电流与电阻的关系时( )
下列事例属于控制传染源的是( )
— Would you like to fly a ____ with me?
— Sorry, I can't. I have to do my ____.