Adjectives are descriptive words that describe other words and answer a question.
Thus, in your sentence, the adjective is the word red, as is tells the reader what color the shirt is.
Answer:
D) The ending is ambiguous
Explanation:
It is not known whether the princess's lover opened the door to be devoured by the tiger or the door to the lady he shall wed.
The narrator lets the reader interpret how the story ends with questions such as, "Now, the point of the story is this: Did the tiger come out of that door, or did the lady?" and "And so I leave it with all of you: Which came out of the opened door, --the lady, or the tiger?"
I hope this helped :)