Option 1 (91st Amendment) -> Enacted in 2003, introduced the 15% cap on Council of Ministers and strengthened anti-defection provisions.
Option 2 (93rd Amendment) -> Enacted in 2005, related to reservation for OBCs in educational institutions.
Option 3 (95th Amendment) -> Enacted in 2009, extended reservation for SCs and STs in legislatures.
Option 4 (99th Amendment) -> Enacted in 2014, established the National Judicial Appointments Commission (NJAC).
Hence, 91st Amendment -> This landmark amendment (2003) was aimed at reforming the political system by capping ministerial positions at 15% of the total Lok Sabha strength to prevent oversized cabinets and also strengthened the anti-defection law by disqualifying defectors from holding ministerial positions -> correct