The answer to the first is C. Elle s'est lavée les mains, or "she washed her hands." I'm not 100 percent sure about this one, but I'm pretty certain. Anyway, when an auxiliary verb is etre, which it is in this case, the following verb must match the subject in gender and number. So laver is the main verb, and because the subject is Elle, the singular feminine version would be lavée. And therefore, the answer is C.
The answer to the second is B. Nous sommes venus, which means "we came." The reason you use the verb etre instead of avoir is because venir is a Vandertramp verb.
