Step 1: Commission and recommendation.
The Mandal Commission (Second Backward Classes Commission), set up in 1979 under PM Morarji Desai and chaired by B. P. Mandal, recommended 27% reservation for OBCs in central services, taking total reservations to 49.5%.
Step 2: Implementation decision.
On 7 August 1990, PM V. P. Singh announced implementation for recruitment to the Central Government services—this is the landmark act asked in the question.
Step 3: Judicial calibration.
In {Indra Sawhney (1992)}, the Supreme Court largely upheld OBC reservation, introduced the creamy layer exclusion, and capped total reservations at 50% (with limited exceptions).
Step 4: Conclude.
\[
\boxed{\text{V. P. Singh (Option A) implemented the Mandal recommendations in 1990.}}
\]