What is the meaning of “distinct,” as used in the first paragraph of the passage?

The author uses the word “distinct” to suggest that the monarch’s coloration is unique, and sets it apart from other butterflies, which is why we’re able to immediately picture what it looks like.
Sometimes confusing is incorrect. The context suggests that “distinct” means something that is easily recognized by people, such as the Monarch butterflies’ coloring. Their colors are not something that confuses people.
Quite ordinary is incorrect. The context suggests that “distinct” means something that is easily recognizable. If it was “quite ordinary,” you would not be able to easily think of what a Monarch butterfly looks like because it’s not memorable.
Extremely large is incorrect. From the context, we can infer that “distinct” does not mean “extremely large” because we know that the passage is talking about a butterfly and no other details suggest anything about its size.