Hydrocarbon P undergoes cracking to produce compound Q and hydrogen. Compound R is made by the addition polymerisation of compound Q. Which homologous series do P, Q and R each belong to?
- Aalkene: P only; alkane: Q and R
- Balkene: Q only; alkane: P and R
- Calkene: P and Q; alkane: R only
- Dalkene: P and R; alkane: Q only