Explanation:

- Option 1: Reduced by the Magistrate

- Typically, once a bail amount is set by a Magistrate, it is not reduced by the same authority. The Magistrate can review the conditions, but reduction requests usually escalate to higher courts.

- Option 2: Reduced by the Court of Sessions

- The Court of Sessions can review and potentially reduce the bail amount set by a Magistrate, as it is a higher judicial authority.

- Option 3: Reduced by the High Court

- The High Court has the jurisdiction to reduce bail, exercising its powers for revision or appeal.

- Option 4: Only (b) & (c)

- This suggests only the Court of Sessions and High Court can reduce the bail amount.

The correct answer is:

- Option 4: Only (b) & (c).