Why might an author choose to paraphrase a source?

a. to provide a citation for an authoritative source
b. to share another's ideas while maintaining his own style
c. to introduce words that are unique or unusual
d. to give credit to the original author of the ideas

Though A and D are correct in what you must do while paraphrasing, they don't explain why an author might choose to paraphrase a source. Also, you don't paraphrase a source because you want to use unique or unusual words so C is out. That leaves you with B. I hope this helps!