Final answer:
The correct answer is D. Enigmatic because it means mysterious or puzzling. Grace Kelly was known for keeping her private life secretive and therefore fans found it challenging to know what she was really like.
Step-by-step explanation:
The correct answer is D. Enigmatic because it means mysterious or puzzling. In the given sentence, the blank should be filled with a word that describes grace Kelly's personality as difficult to understand. The word enigmatic accurately portrays this quality. Grace Kelly was known for keeping her private life secretive and therefore fans found it challenging to know what she was really like.