Concept:
Critical Tiger Habitat (CTH) refers to core areas of tiger reserves that are kept inviolate for tiger conservation.
Step 1:Recall key facts.
Among the listed reserves,
Nagarjunsagar Srisailam Tiger Reserve is the
largest tiger reserve in India and has the largest CTH area.
Step 2:Compare options.}
- Corbett $\rightarrow$ Large but smaller than Nagarjunsagar Srisailam
- Ranthambore $\rightarrow$ Much smaller reserve
- Sunderbans $\rightarrow$ Unique mangrove ecosystem but smaller CTH
Final Answer:
\[
{\text{Nagarjunsagar Srisailam}}
\]