Answer:
A and B are correct
Explanation:
Option C states that the MSRB can be invoked by a municipal securities professional against a non-municipal securities professional with or without an arbitration agreement, however the correct thing is that it can only be invoked against a non-municipal securities professional as long as there exist an arbitration agreement. Hence Option C is wrong.
Option D states that it applies to claims and dispute from both municipal and non-municipal securities activities, when in real sense it only applies to municipal securities disputes.
Option A and B are therefore the only correct options.