Which ketone isomer of C7H14O\text{C}_7\text{H}_{14}\text{O}C7H14O produces the smallest number of peaks in its 13C^{13}\text{C}13C NMR spectrum?
Heptan-4-one, CH3CH2CH2COCH2CH2CH3\text{CH}_3\text{CH}_2\text{CH}_2\text{COCH}_2\text{CH}_2\text{CH}_3CH3CH2CH2COCH2CH2CH3
5-Methylhexan-3-one, CH3CH2COCH2CH(CH3)2\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH(CH}_3)_2CH3CH2COCH2CH(CH3)2
2,4-Dimethylpentan-3-one, (CH3)2CHCOCH(CH3)2\text{(CH}_3)_2\text{CHCOCH(CH}_3)_2(CH3)2CHCOCH(CH3)2
4,4-Dimethylpentan-2-one, CH3COCH2C(CH3)3\text{CH}_3\text{COCH}_2\text{C(CH}_3)_3CH3COCH2C(CH3)3