Correct Answer: B
Explanation:
The clue for this sentence is "the lovely rainbows they produce," which suggests that the blank should be filled by a word meaning colorful. Both iridescent and pavonine mean exactly that. Even if you don't agree that the blank necessarily refers to rainbows of color, the missing word does have to agree with beautiful due to the trigger and, and none of the other four options does: Anodyne means eliminating physical pain, monocoque means constructed in one piece, parietal mean college-related, and saturnine means gloomy.