B is the correct answer. I just had a test on this type of questions
I answered it already in the question thingy box!
Translating the sentence, we get something along the lines of Raul ____ the pen to write. There's one word we can see falls into the blank, and that's used. Now all wee need to do is translate used into Spanish. One way to say used in Spanish is usado, so usado is the word that best completes the sentence.
