Reference Potential of Earth and Electric Potential of Charged Sphere

To determine the correct option, let us analyze both statements individually:

1. Analysis of STATEMENT-1:
   In practical electrical circuits, the Earth is used as an infinite reservoir of charge. Grounding a conductor allows charge to flow between the conductor and the Earth until they reach the same potential. Due to its enormous size, adding or removing finite amounts of charge from the Earth does not change its potential noticeably. Hence, for practical purpose, the Earth's potential is chosen as the reference level of zero potential ($V_{\text{Earth}} = 0$).
   Therefore, STATEMENT-1 is True.

2. Analysis of STATEMENT-2:
   For a spherical conductor or a thin spherical shell of radius $R$ carrying a charge $Q$ uniformly distributed over its surface, the electric field outside the sphere ($r \ge R$) is given by Gauss's Law as:
   $E(r) = \frac{Q}{4 \pi \varepsilon_0 r^2}$
   Taking potential at infinity to be zero ($V(\infty) = 0$), the electric potential $V$ at the surface ($r = R$) is obtained by integrating the electric field:
   $V = -\int_{\infty}^R E(r) \, dr = -\int_{\infty}^R \frac{Q}{4 \pi \varepsilon_0 r^2} \, dr = \frac{Q}{4 \pi \varepsilon_0 R}$
   Therefore, STATEMENT-2 is True.

3. Relationship between STATEMENT-1 and STATEMENT-2:
   Modeling the Earth as a spherical conductor of radius $R_{\text{Earth}} \approx 6.4 \times 10^6 \text{ m}$, the potential acquired by the Earth when a charge $Q$ is transferred to it is:
   $V_{\text{Earth}} = \frac{Q}{4 \pi \varepsilon_0 R_{\text{Earth}}}$
   Because $R_{\text{Earth}}$ is exceptionally large, the denominator $4 \pi \varepsilon_0 R_{\text{Earth}}$ (which represents the Earth's electrical capacitance $C \approx 711 \ \mu\text{F}$) is very large. Consequently, for any realistic value of charge $Q$ encountered in laboratory or practical circuits:
   $V_{\text{Earth}} \approx 0$
   Thus, the expression in STATEMENT-2 directly explains why the Earth maintains a practically constant, zero potential irrespective of the charge transferred to it. Hence, STATEMENT-2 is the correct explanation for STATEMENT-1.

Conclusion:
STATEMENT-1 is True, STATEMENT-2 is True; STATEMENT-2 is a correct explanation for STATEMENT-1.

Correct Option: (A)