The question is really testing whether you can tell apart the person who named a concept from the people who made it work in practice.
Since two of the four choices are judges known for applying PIL and one is a foreign scholar writing on a different system, only Prof. Upendra Baxi remains as the person who first used the term.
The correct option is Prof. Upendra Baxi.
Looking at this chronologically helps separate the origin of the phrase from its later judicial growth.
Placed on a timeline, the scholarly use of the term precedes its heavy judicial application, which points to the academic rather than either judge.
Hence, the correct answer is Prof. Upendra Baxi.