Assuming you had to choose between:
- A) more exciting
- B) exciting
- C) excitinger
- D) most exciting
The answer is: "Many critics described the movie's final scene as the most exciting (D) car chase that has ever been shot."
The presence of the word "the" before the adjective indicates that you have a superlative (the most something).
"Exciting" contains 3 syllables, which is too many for the superlative to take the form of a suffix -est at the end of the adjective (as in "the prettiest"). Therefore, the answer is "the most exciting."