Which of the following correctly lists these nitrogen-containing compounds in order of increasing base strength (weakest base first)?
CH3CONH2,C6H5NH2,NH3,(CH3CH2)2NH \text{CH}_3\text{CONH}_2, \quad \text{C}_6\text{H}_5\text{NH}_2, \quad \text{NH}_3, \quad (\text{CH}_3\text{CH}_2)_2\text{NH} CH3CONH2,C6H5NH2,NH3,(CH3CH2)2NHC6H5NH2<CH3CONH2<NH3<(CH3CH2)2NH\text{C}_6\text{H}_5\text{NH}_2 < \text{CH}_3\text{CONH}_2 < \text{NH}_3 < (\text{CH}_3\text{CH}_2)_2\text{NH}C6H5NH2<CH3CONH2<NH3<(CH3CH2)2NH
CH3CONH2<C6H5NH2<NH3<(CH3CH2)2NH\text{CH}_3\text{CONH}_2 < \text{C}_6\text{H}_5\text{NH}_2 < \text{NH}_3 < (\text{CH}_3\text{CH}_2)_2\text{NH}CH3CONH2<C6H5NH2<NH3<(CH3CH2)2NH
(CH3CH2)2NH<NH3<C6H5NH2<CH3CONH2(\text{CH}_3\text{CH}_2)_2\text{NH} < \text{NH}_3 < \text{C}_6\text{H}_5\text{NH}_2 < \text{CH}_3\text{CONH}_2(CH3CH2)2NH<NH3<C6H5NH2<CH3CONH2
CH3CONH2<(CH3CH2)2NH<NH3<C6H5NH2\text{CH}_3\text{CONH}_2 < (\text{CH}_3\text{CH}_2)_2\text{NH} < \text{NH}_3 < \text{C}_6\text{H}_5\text{NH}_2CH3CONH2<(CH3CH2)2NH<NH3<C6H5NH2