I think the idea here is that each of the four witnesses gave one of the numbers in the question. They all agree that it is 3*J*Z. 3 witnesses (all except A)

I think the idea here is that each of the four witnesses gave one of the numbers in the question. They all agree that it is 3*J*Z. 3 witnesses (all except A) agree that the second digit was 5. 3 witnesses (all except B) agree that the third digit was 1. 3 witnesses (all except C) agree that the second letter was an R. Every letter/number that D gives is corroborated by two other witnesses (though a different two each time), so D is most likely to be correct.