General: Can Mary play two musical instruments well?
Tag question: Mary can play two musical instruments well, can't she?
Special 1: How many musical instruments can Mary play well?
Special 2: What musical instruments can Mary play well?
Special 3: How well can Mary play two musical instruments?
Может быть, один из специальных вопросов должен быть к подлежащему? Who can play two musical instruments well?