Step 1: Ask where the RCH programme draws its planning boundary. The answer is the district - it is the administrative unit at which RCH inputs are designed and tracked.
Step 2: RCH deliberately avoids a one-size-fits-all model. Care components stay constant, but resource intensity scales with need, so lagging districts get additional support and stronger districts get upgraded facilities.
Step 3: The classification into A, B, and C groups uses crude birth rate and female literacy, both measured district-wise, with phased rollout over three years. This confirms the district as the inclusive last point of the programme, ruling out the smaller sub-centre, Anganwadi, and Taluka.
\[\boxed{\text{District}}\]