A seems like the right answer. Normally if a sentence sounds right, it is.
B is wrong because it makes it seem like she finished a book report with her family. The words are all mixed up.
C is wrong because it says she looked forward to having just finished... it doesn't make sense. She was looking forward to a relaxing weekend, not the report.
D is wrong because the words are all mixed up and doesn't make sense.
Hope this helps!
