My approach: I have reached to this conclusion within 45 seconds:- 1. As "they" does not have clear reference, all the options having "they" can be easily eliminated. So, A, C, and E are out. 2. Now, we are in between B and D. We should bear in mind that modal auxiliaries should not be replaced by "be verbs". It has been done in D. Using "be verb" in stead of "modal", D has distorts the meaning of the sentence.
Look: Can you play cricket? [It means that I have doubt on your ability to play cricket.] Do you play cricket? [It means that I have no doubt that you can play cricket. My question is whether you play or not.]