The correct option is D III < II < I
Convert conjugate base into acid by adding H⊕, find the acidic character and then reverse the order after removing H⊕ ions that would be the order for basic character.
HC≡CH is most acidic because of the presence of sp hybridized C as acidity is directly proportional to % of s-character. In between N and C, N is more electronegative than C. So, acidity of NH3>CH4.
Acidity: HC≡CH>NH3>CH4
Basicity: HC≡C⊖<⊖NH2<⊖CH3
The lower the value of pKb, the stronger is the base.
pKb order:
III < II < I