Dyslexia involves primarily the reversal of which types of characters?

Dyslexia primarily involves difficulties with the processing of written language, particularly concerning the visual representation of letters. Reversal of letters often manifests as a hallmark characteristic of dyslexia, where individuals may confuse letters that have similar shapes or sounds, such as "b" and "d" or "p" and "q".

This confusion can extend to numbers as well, as some individuals with dyslexia may also experience difficulty distinguishing between similarly shaped numbers, leading to similar types of reversals. These challenges are tied to the visual and cognitive processing involved in reading, making the specific focus on letters and numbers particularly relevant to dyslexia.

In contrast, the other types mentioned, such as words, sentences, symbols, sounds, and music, do not encapsulate the primary challenges faced by individuals with dyslexia. Dyslexia's core issues are specifically centered on the letter-level processing involved in reading, which is why the reversal of letters and, to a lesser extent, numbers is the correct answer.