Step 1: Compare the meaning of each statement.
- (A) “One of the greatest” ⇒ superlative, but includes others in the same group.
- (B) “Greater than many” ⇒ comparative; implies many are less great, but not necessarily all.
- (C) “The greatest” ⇒ absolute superlative — no one else equals him.
- (D) “Very few kings were as great” ⇒ implies very small number match him, close to (A).
Step 2: Identify the odd one.
Options (A), (B), and (D) allow for the possibility that others were close in greatness. (C) stands out because it claims an absolute, unmatched position.
\[
\boxed{\text{(C) Ashoka was the greatest king}}
\]