b
Order of basic strength is
$\underbrace {C{H_3} - C{H_2} - N{H_2}}_{ + \,I}$ $ > \,\underbrace {Ph}_{ - \,I} - C{H_2} - N{H_2}$ $\underset{\begin{smallmatrix}
delocalise \\
l.p.
\end{smallmatrix}}{\mathop{>\,Ph\,-\,\underset{\scriptscriptstyle\centerdot\centerdot}{N}{{H}_{2}}}}\,$