Amino acids with an amide on the side chain do not produce basic solutions ...

You need to look at the functional groups carefully because an amide starts out looking like an amine, but has the carbon double bond oxygen which changes the property. Amides are not basic.

therefore, option C is correct......

the correct ans is C.

the basicity of compound depend on its tendency of holding more electrons on basic group itself.

here,

in III;  N has its lone pair and two CH₃ groups are exerting +I effect. thus increasing the e^- density on NH

I;   due to two two NH group there is resonance and e^-s are moving. none of both has complete hold of it. there is +i effect also.

II;  CH₃CH₂ has less +I effect on the present NH_{2 group.}

IV;  O is more electronegative than N. so it pulls the electrons towards itself through reso. forming double bond N==C and single bond O---C. IT IS LEAST BASIC.

therefore, III>I>II>IV.