Step 1: Identify the conflict.
Sri Lanka experienced protracted ethnic tensions between the Sinhalese majority and Tamil minority culminating in civil war (1983–2009), often framed as racial/ethnic conflict.
Step 2: Compare options.
The intensity, duration, and characterization of conflict in Sri Lanka make it the most appropriate choice among the listed South Asian countries.
Step 3: Conclude.
\[
\boxed{\text{Sri Lanka (Option C).}}
\]