Physics · Electrostatic Potential

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Sensitive electronic instruments are shielded from external electrostatic fields by enclosing them inside a hollow metallic box. Reason (R): The electrostatic field inside an empty closed metallic cavity is always zero, regardless of the size or shape of the cavity. In the light of the above statements, choose the correct answer from the options given below:

1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
3. is true but (R) is false.
4. is false but (R) is true.