Based on the poem "A Motif" by Kirk Robinson, the reader can infer that D: The speaker understands music is probably true.
The poem speaks about a musical motif, which is a repeating musical phrase or pattern. The speaker describes the motif as "a thing of beauty" and "a joy forever." The speaker also talks about how the motif "can take you places" and "touch your soul."
These lines suggest that the speaker has a deep understanding and appreciation of music. The speaker understands the power of a musical motif to evoke emotions and transport the listener to different places. Therefore, the statement that the speaker understands music is the most likely inference that can be made from the poem.