It's asistimos. You should use a Spanish dictionary some of the other words don't exist.
Answer:
For the first three blanks, I would say use "lo" because, it means 'it', "i can find it if i search well. I think -- where can I find it?". If you just plug the words into the sentence it would all come together! For the last blank use 'la, los,or las" whichever floats your boat :) Explanation:
correct answer:
Beatriz nos preparó el archivo para
nosotros.
