While the author's early novels were often criticized for their ______ plotlines and undeveloped characters, her later works displayed a remarkable ______ in narrative complexity and psychological depth.

✓ Correct Answer: Option C

The first blank needs a word indicating a flaw in early novels, contrasted with later improvement. 'Rudimentary' (basic, undeveloped) fits. The second blank needs a word indicating improvement, so 'sophistication' (development, refinement) creates a logical progression.