— Helen, would you like to go to the park with me?
— .
A:Sorry, I wouldn't
B:Yes, I'd love
C:That's right
D:That's a good idea
若复数2+ai1-ia∈R是纯虚数(i是虚数单位),则a的值为( )
日本工业发展的不利条件是( )
读图,回答下列问题.