The diagram shows a section of an addition polymer.

Which monomer is used to make this polymer?
CH2=CHCH3\mathrm{CH_{2}{=}CHCH_{3}}CH2=CHCH3
CH3CH=CHCH3\mathrm{CH_{3}CH{=}CHCH_{3}}CH3CH=CHCH3
CH2=C(CH3)2\mathrm{CH_{2}{=}C(CH_{3})_{2}}CH2=C(CH3)2
CH2=CHCH2CH3\mathrm{CH_{2}{=}CHCH_{2}CH_{3}}CH2=CHCH2CH3
63 exam-style questions on OCR GCSE Chemistry 6.2 Organic chemistry, covering 6.2.1 Crude oil and fractional distillation, 6.2.2 Cracking and dependence on hydrocarbons, 6.2.3 Functional groups and homologous series, 6.2.4 Reactions of alkanes, alkenes and alcohols, 6.2.5 Addition polymerisation and repeat units, 6.2.6 Naturally occurring polymers, 6.2.7 Chemical cells and fuel cells, and 6.2.8 Condensation polymerisation and how to make one. Each one has a worked solution and a mark scheme showing where the marks go.