The radii of two cylinders are in the ratio 3 : 5.

Given that

$r_{1}: r_{2}=3: 5$ and $h_{1}: h_{2}=2: 3$

Then,

The ratio of C.S.A. of cylinders

$\frac{s_{1}}{s_{2}}=\frac{2 \pi r_{1} h_{1}}{2 \pi r_{2} h_{2}}$

$\frac{s_{1}}{s_{2}}=\left(\frac{r_{1}}{r_{2}}\right) \times\left(\frac{h_{1}}{h_{2}}\right)$

$=\frac{3}{5} \times \frac{2}{3}$

$\frac{s_{1}}{s_{2}}=\frac{2}{3}$

$s_{1}: s_{2}=2: 5$

Hence, the correct answer is choice (a).