The value of $\lim_{n \to \infty} \frac{\sum_{r=0}^{n} {}^{2n}C_{2r} \times 3^{r}}{\sum_{r=0}^{n-1} {}^{2n}C_{2r+1} \times 3^{r}}$ is\\ (a) 0\\ (b) 1\\ (c) $\sqrt{3}$\\ (d) $(\sqrt{3}-1)/(\sqrt{3}+1)$