Plagiarism is a BIG no no. If you're going to read and use someones information on a subject, make sure to tweak it. (Ex. If a piece of information says, "Thomas Edison was a great inventor and a huge genius." You can tweak it by saying., "Thomas Edison was a magnificent inventor and an enormous mastermind." Plagiarism can get you in BIG trouble for; cheating, copying and such.
A, sister’s is short for ‘sister is,’ which does t make sense in the context of the sentence. D doesn’t have any punctuation, which is actually what it need to technically be an actual word. So A is your answer.