Step 1: Understanding the investigation.
The Justice S.N. Phukhan Commission was set up to investigate the Stamp Paper scam, also known as the "Stamp Paper Scam" or "Telgi Scam." This scam involved the illegal printing and distribution of stamp papers in India.
Step 2: Analyzing the options.
- (a) Tehelka: Incorrect. The Tehelka scandal was a separate political scandal and not under investigation by this commission.
- (b) Stamp Paper: Correct. The Stamp Paper scam, or Telgi scam, is the case that Justice S.N. Phukhan Commission investigated.
- (c) Cooperative Bank: Incorrect. While there have been several cooperative bank scandals, they were not the focus of this particular commission.
- (d) US-64: Incorrect. The US-64 scam was investigated by other bodies, not the Phukhan Commission.
Step 3: Conclusion.
The correct answer is (b), as the Justice S.N. Phukhan Commission was investigating the Stamp Paper scam.