—______ I park my car here for a while?
—No, you mustn't. Do you see the sign"NO PARKING"?
A:Would
B:May
C:Must
D:Should
我国的纸币最早出现于( )
已知水稻的抗病(R)对感病(r)为显性,有芒(B)对无芒(b)为显性.现有抗病有芒和感病无芒两个品种,要想选育出稳定遗传的抗病无芒的新品种,从理论上分析,不可行的育种方法为( )