Which Modifications Reduce Receptor Conductance

Which modifications reduce receptor conductance?

A) substitution of 2′ threonine (T) with a smaller hydrophilic residue
B) substitution of 2′ threonine (T) with a larger hydrophilic residue
C) substitution of 2′ threonine (T) with a smaller hydrophobic residue
D) substitution of 2′ threonine (T) with any polar residue
E) substitution of 2′ threonine (T) with a larger hydrophobic residue