Step 1: Section 25 rule.
Section 25 of the Evidence Act states that a confession made to a police officer shall not be proved as against a person accused of any offence.
Step 2: Scope.
This bar applies regardless of whether the confession relates to the same crime or another crime. Hence, options (a), (b), and (c) do not capture the correct principle.
Step 3: Conclusion.
Therefore, the correct answer is (d).