Which of these equations represents a reaction that proceeds via a nucleophilic addition-elimination mechanism?
CH3COCH3+HCN→CH3C(OH)(CN)CH3\text{CH}_3\text{COCH}_3 + \text{HCN} \rightarrow \text{CH}_3\text{C(OH)(CN)CH}_3CH3COCH3+HCN→CH3C(OH)(CN)CH3
CH3CH2CH2Br+NH3→CH3CH2CH2NH2+HBr\text{CH}_3\text{CH}_2\text{CH}_2\text{Br} + \text{NH}_3 \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{NH}_2 + \text{HBr}CH3CH2CH2Br+NH3→CH3CH2CH2NH2+HBr
(CH3CO)2O+C6H5OH→CH3COOC6H5+CH3COOH(\text{CH}_3\text{CO})_2\text{O} + \text{C}_6\text{H}_5\text{OH} \rightarrow \text{CH}_3\text{COOC}_6\text{H}_5 + \text{CH}_3\text{COOH}(CH3CO)2O+C6H5OH→CH3COOC6H5+CH3COOH
(CH3)3CBr+KOH→(CH3)2C=CH2+KBr+H2O(\text{CH}_3)_3\text{CBr} + \text{KOH} \rightarrow (\text{CH}_3)_2\text{C}=\text{CH}_2 + \text{KBr} + \text{H}_2\text{O}(CH3)3CBr+KOH→(CH3)2C=CH2+KBr+H2O