What did the speaker struggle to hear?

The speaker struggled to hear themselves, which implies an internal conflict, perhaps related to their own thoughts or self-expression. This situation can occur in contexts where a person is in a noisy environment or feeling overwhelmed, making it difficult to focus on their own voice or thoughts.

On the other hand, the other selections do not align with the context of personal struggle. The music, teacher, and peers all represent external sources of sound that the speaker might be able to hear despite distractions or noise. The correct choice reflects an introspective challenge rather than just a simple difficulty with outside noises. Thus, the focus is on the speaker's own internal dialogue rather than the external environment.