### Step-by-Step Derivation & Verification: 1. **Topological Composition**: - Input stage: Two non-inverting buffers cross-coupled via a single gain-setting resistor $R_G$. Differential gain is $1 + \frac{2R_1}{R_G}$, while common-mode gain is unity ($A_{\text{cm1}} = 1$). - Output stage: Differential difference amplifier with gain $R_3 / R_2$ designed to cancel common-mode components. 2. **Key Advantages**: - Both inputs ($V_1, V_2$) look directly into op-amp non-inverting terminals, achieving ultra-high input resistance ($R_{\text{in}} > 10^9\,\Omega$) without loading delicate sensors. - Delivers exceptionally high CMRR (
gt; 100\text{ dB}$), rejecting identical noise on both input leads. 3. **Conclusion**: High CMRR with high differential input impedance. Option (A) is correct.