C

To find the effective resistance between points A and B in the given circuit, we first analyze the configuration of the resistors.

1. **Resistors in Series and Parallel**: Identify which resistors are in series and which are in parallel. The circuit shows: - Resistors 3 ohms (PA, AQ, and RS) directly between points A and B. - Two sets of resistors (6 ohm and 3 ohm resistors) in parallel between the upper sets (PQRS) of the diagram.

2. **Calculating Effective Resistance**: - The two 6 ohm resistors are in parallel: $$ R_p = \frac{R_1 \times R_2}{R_1 + R_2} = \frac{6 \times 6}{6 + 6} = 3 \text{ ohms} $$ - This 3 ohm result is effectively in series with the two 3 ohm resistors. - Total for this branch will be: 3 ohms (from 6 ohm parallel) + 3 ohms (series) + 3 ohms (another 3 ohm) - Simplifying gives us 3 + 3 + 3 = 9 ohms.

3. **Final Effective Resistance**: Therefore, the total effective resistance across points A and B is **9 ohms**. The final answer matches with option C.