Allow to Filter or Recommend?

Consider a large question-bank site. The questions are tagged with course and topics and have meta-ratings like difficulty, frequency in exams etc. A user can open the question and do it, and the site can recommend other related questions based on it. But, what will the user like more? Assume that there are large number of questions, and there is a powerful filter tool implemented.

A) Filter and Explore the Questions he wants (Like Amazon/Ebay)

B) Get a Sorted List of Recommended Questions (Like Youtube)

C) Mix of Both (but in what proportion?)