Which structural formula represents propene?
CH3CH2CH3\text{CH}_3\text{CH}_2\text{CH}_3CH3CH2CH3
CH3CH2CH2OH\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}CH3CH2CH2OH
CH2=CHCH2CH3\text{CH}_2\text{=CHCH}_2\text{CH}_3CH2=CHCH2CH3
CH3CH=CH2\text{CH}_3\text{CH=CH}_2CH3CH=CH2