Volume of the cone $V=\frac{1}{3}\pi r^{2}h$
Here only radius change so we can write $V\propto r^{2}$
$r\rightarrow r+\frac{50}{100}r \implies r\rightarrow 1.5r$
New volume $ {V}'\propto (1.5r)^{2} \propto 2.25r^{2}$
Percentage changes in volume $=\frac{2.25r^{2}-r^{2}}{r^{2}}\times 100=1.25\times 100=125\%$
So, correct option is $(C)$