b
$\begin{array}{l}
Given,\,{u_1} = {u_2} = u,\,\,\,\,\,\,{\theta _1} = {60^ \circ },\,\,{\theta _2} = {30^ \circ }\\
In\,1st\,case,\,we\,know\,that\,range\\
{R_1} = \frac{{{u^2}\sin 2\left( {{{60}^ \circ }} \right)}}{g} = \frac{{{u^2}\sin {{120}^ \circ }}}{g}\\
\,\,\,\,\,\,\, = \frac{{{u^2}\sin \left( {{{90}^ \circ } + {{30}^ \circ }} \right)}}{g}\\
= \frac{{{u^2}\left( {\cos {{30}^ \circ }} \right)}}{g} = \frac{{\sqrt 3 {u^2}}}{{2g}}
\end{array}$
$\begin{array}{l}
In\,IInd\,case\,when\,\,{\theta _2} = {30^{ \circ \,}},\,then\\
{R_2} = \frac{{{u^2}\sin {{60}^ \circ }}}{g} = \frac{{{u^2}\sqrt 3 }}{{2g}} \Rightarrow {R_1}{R_2}\\
\left( {we\,get\,same\,value\,of\,ranges} \right).
\end{array}$
