Answer:
C. Sondra practiced her speech for two hours last night; furthermore, she woke up at 5:30 a.m. to review and practice it.
Step-by-step explanation:
A and B clearly use the semicolon incorrectly, whereas there doesn't appear to be one in D at all. In A and B, the semicolon is placed in the middle of a sentence where they could be removed. When it is placed between clauses, each of the two parts of the sentence, if considered on their own, would make incomplete sentences. So a comma should replace the semicolon in those places.