Step 1: Understanding the Mandal Commission Report
The Mandal Commission, formed in 1979, recommended reserving 27\% of government jobs for people from the Other Backward Classes (OBCs). The report was implemented in 1990, which caused widespread protests and debates.
Step 2: Analyzing the Options
- (A) Indira Gandhi: Incorrect. Indira Gandhi was the Prime Minister in the 1960s and 1970s, but not during the implementation of the Mandal Commission's report in 1990.
- (B) Rajiv Gandhi: Incorrect. Rajiv Gandhi was the Prime Minister until 1989 but did not implement the Mandal Commission report.
- (C) Chandrashekhar: Incorrect. Chandrashekhar was Prime Minister in 1990-1991 but did not implement the Mandal Commission's report.
- (D) Vishwanath Pratap Singh: Correct. Vishwanath Pratap Singh, the Prime Minister of India in 1990, implemented the Mandal Commission’s report, which led to the reservation of 27% of government jobs for OBCs.
Step 3: Conclusion
Vishwanath Pratap Singh, as the Prime Minister of India in 1990, implemented the Mandal Commission's report.
\[
\boxed{\text{Correct Answer: (D) Vishwanath Pratap Singh}}
\]