Which word's spelling is the result of euphony?

Euphony refers to a harmonious, pleasant sound effect produced when certain phonetic elements are combined, often making the pronunciation of a word more agreeable and easier to articulate. The word "illegible" exemplifies this concept, as its spelling incorporates phonetic elements that contribute to its smooth and flowing sound, enhancing its verbal appeal.

In contrast, the other words do not exhibit this deliberate crafting for euphony in the same way. For instance, "muscular," while straightforward and easy to pronounce, does not have the same euphonic qualities as "illegible." Similarly, "knowledge" and "chlorophyll" also consist of sounds and letters that do not enhance the overall auditory experience in comparison to "illegible." Ultimately, "illegible" stands out as having a spelling that effectively embodies euphony, making it the best choice among the options presented.