X, Y and Z are three hydrocarbons. $X$: $\text{CH}_2=\text{CH}_2$\quad $Y$: $\text{CH}_3-\text{CH}=\text{CH}_2$\quad $Z$: $\text{CH}_3-\text{CH}_2-\text{CH}=\text{CH}_2$ 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