Answer:
No error.
Explanation:
Punctuation errors, be it in the use of the punctuation signs, or capitalizations, etc. forms one of the most important aspects of correct sentences. And not only that, the subject-verb agreement, the use of the adverbs and adjectives also constitute a correct sentence.
In the given sentence <em>"[A]lthough Sonia dances gracefully, her brother Tomas moves clumsily"</em>, there is no error. The adverbs "gracefully" and "clumsily" are correct, describing the way the characters move.
Thus, there is no error in the given sentence.
