X, Y and Z are three hydrocarbons. $X$: $\text{CH}_2{=}\text{CH}_2$, $Y$: $\text{CH}_3{-}\text{CH}{=}\text{CH}_2$, $Z$: $\text{CH}_3{-}\text{CH}_2{-}\text{CH}{=}\text{CH}_2$. What feature do compounds X, Y and Z all share?
- A1, 2 and 3
- B1 and 2 only
- C1 and 3 only
- D2 and 3 only