Which compound produces only one singlet and two triplets in its 1H^1\text{H}1H NMR spectrum?
CH3CH2COOCH3\text{CH}_3\text{CH}_2\text{COOCH}_3CH3CH2COOCH3
ClCH2CH2COOCH3\text{ClCH}_2\text{CH}_2\text{COOCH}_3ClCH2CH2COOCH3
CH3CH2CH2COOCH3\text{CH}_3\text{CH}_2\text{CH}_2\text{COOCH}_3CH3CH2CH2COOCH3
ClCH2CH2CH2COOCH3\text{ClCH}_2\text{CH}_2\text{CH}_2\text{COOCH}_3ClCH2CH2CH2COOCH3