c
Diethyl ether \((CH_3CH_2)_2O\) is resistant to nucleophilic attack because because it does not have an electron deficient carbon.

\(\mathop {{C_2}{H_5} - O - {C_2}{H_5}}\limits_{Ether} \)       \(\mathop {\begin{array}{*{20}{c}}
  {O\,\,\,\,} \\ 
  {||\,\,\,\,} \\ 
  {C{H_3} - C - OC{H_3}} 
\end{array}}\limits_{Methyl\,\,acetate} \)

\(\mathop {C{H_3} - C \equiv N}\limits_{Acetonitrile} \)       \(\mathop {\begin{array}{*{20}{c}}
  O \\ 
  {||} \\ 
  {C{H_3} - C - N{H_2}} 
\end{array}}\limits_{Acetamide} \)