Step 1: Trace the origin.
The grassroots RTI movement began in Rajasthan in the early 1990s, led by Mazdoor Kisan Shakti Sangathan (MKSS) at Devdungri. Villagers demanded access to muster rolls and bills to expose leakages in local works.
Step 2: Why Rajasthan is credited.
Jan Sunwais (public audits) pioneered by MKSS institutionalized social audit practices, forcing disclosure and inspiring state and national laws.
Step 3: Clarify common confusion.
Tamil Nadu did pass one of the earliest state RTI laws in 1997, but the {movement’s genesis} is credited to Rajasthan. The national RTI Act came in 2005.
Step 4: Conclude.
\[
\boxed{\text{Rajasthan (Option A) is where the RTI movement started.}}
\]