If the limelight of a movie was on a character who had one defect, the scriptwriter might have been making an allusion to .

Achilles

Explanation:

A faulty character is likely to be an allusion to Achilles. This is because Achilles was a man who was bathed in the river Styx and was left invulnerable. However, he had a flaw. His heel was not washed in the river and it became a completely fragile place. For this reason, a character in a movie who has a single flaw might allude to Achilles.

It is important to remember that allusion is a figure of speech that allows a writer to make references to things, people and places that are not part of his/her text, but which have a special meaning when added to the text.

i think that it is letter d.