J and M are the only two sapphires. That triggers rule 2. We have one ruby, and therefore three topazes.
One of the topazes is W, thanks to rule 4.
We also know we can’t have H and Z.
We need two other topazes. Since we can’t use Z, we must have both X and Y instead.
The single ruby can be F or G.
A is wrong. We can only have one ruby.
B is CORRECT. We need X, and we can have F.
C is wrong. If M is in, W is in and H is out.
D is wrong. The question said K isn’t one of the sapphires selected.
E is wrong. If M is in, W is in and Z is out (rules 3-4).
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