Step 1: Understanding the Case.
In *Peoples Union for Democratic Rights Vs Union of India*, Justice Bhagwati expounded the concept of *Public Interest Litigation (PIL)*. The case recognized that any member of the public, especially when acting on behalf of disadvantaged persons, could approach the court for relief under Articles 32 or 226 of the Constitution, even when the affected parties themselves are unable to do so due to their disadvantaged position.
Step 2: Explanation of Other Options.
- (b) Ashok Kumar Pandey Vs State of West Bengal is a case involving the scope of judicial review but does not specifically address PIL in the same context.
- (c) *S. P. Gupta Vs Union of India* deals with judicial independence and the appointment of judges, not with PIL as described in the question.
- (d) Janata Dal Vs H. S. Chowdhary concerns defamation, not PIL.
Step 3: Conclusion.
The correct case is *Peoples Union for Democratic Rights Vs Union of India*, where PIL was expanded to allow individuals to seek justice for the poor and disadvantaged.