parityhome

I notice BBO now offers three ACBL Daylong tournaments for MP and IMP, for example ACBL Daylong (MP) A ACBL Daylong (MP) B ACBL Daylong (MP) C Usually A has the most number of participants, followed by B and then C, although we're free to choose any or all of them to play. Does anybody know why there are three? Is there hidden difference among them?