Explanation

(d) For Lyman series $\frac{1}{\lambda_{\max}} = R\left\lbrack \frac{1}{1^{2}} - \frac{1}{2^{2}} \right\rbrack = \frac{3}{4}R$ and
$\frac{1}{\lambda_{\min}} = R\left\lbrack \frac{1}{1^{2}} - \frac{1}{\infty^{2}} \right\rbrack = \frac{R}{1} \Rightarrow \frac{\lambda_{\max}}{\lambda_{\min}} = \frac{4}{3}$