单项选择题
A.CH2=CHCH3B.CH3CH=CHCH3C.CH3CH=C(CH3)2D.CH2=CH2
A.CH2=CHCH3B.CH3CH=CHCH3C.(CH3)2C=C(CH3)2D.CH2=CH2
A.1种B.2种C.3种D.4种