We were given two triangles, ABC and XYZ. The problem also states that the angles B and Y are congruent, and the sides AB and XY are also congruent. We need to point out which information is missing so that we can prove the triangles are congruent by SAS.
The term SAS stands for Side-Angle-Side, it means that two triangles are similar when they have two congruent Sides and one congruent Angle. Since the problem already said that one side and one angle are congruent, then we only need one more side. From this, we can conclude that the correct option is B.