For better tuning (higher selectivity or sharpness of resonance) in an L-C-R circuit, the Quality Factor (Q-factor) must be high. The Q-factor is given by the formula $Q = \frac{1}{R}\sqrt{\frac{L}{C}}$ . To maximize $Q$, resistance ($R$) should be low, inductance ($L$) should be large, and capacitance ($C$) should be small. Comparing the options:

1. $Q_1 = \frac{1}{20}\sqrt{\frac{1.5}{35\times 10^{-6}}} \approx 10.3$
2. $Q_2 = \frac{1}{25}\sqrt{\frac{2.5}{45\times 10^{-6}}} \approx 9.4$
3. $Q_3 = \frac{1}{15}\sqrt{\frac{3.5}{30\times 10^{-6}}} \approx 22.7$
4. $Q_4 = \frac{1}{25}\sqrt{\frac{1.5}{45\times 10^{-6}}} \approx 7.3$ Option 3 yields the highest Q-value, providing the best tuning.