Which reagents could be used to prepare CH3CONHCH2CH3\text{CH}_3\text{CONHCH}_2\text{CH}_3CH3CONHCH2CH3?
CH3COCl+CH3CH2NH2\text{CH}_3\text{COCl} + \text{CH}_3\text{CH}_2\text{NH}_2CH3COCl+CH3CH2NH2
CH3CONH2+CH3CH2Cl\text{CH}_3\text{CONH}_2 + \text{CH}_3\text{CH}_2\text{Cl}CH3CONH2+CH3CH2Cl
CH3COONa+CH3CH2NH2\text{CH}_3\text{COONa} + \text{CH}_3\text{CH}_2\text{NH}_2CH3COONa+CH3CH2NH2
CH3COCH3+CH3CH2NH2\text{CH}_3\text{COCH}_3 + \text{CH}_3\text{CH}_2\text{NH}_2CH3COCH3+CH3CH2NH2