Question

Anyone know what the answer is ?

Answer 1

A perpendicular bisector
this means the length IJ=JK and the angles IJB, BJK are 90° (and their congruent angles too)

but this does not mean AB=IK, because their lengths can be arbitrary
for a similar reason AJ=IJ is wrong, essentially the same statement but with half lengths
BI=BK is true, because it is a bisector of IK this means the sides IJ=JK and JB is a shared side, therefore also having the same length. We also know IJB and BJK are congruent angles, so all in all these are congruent triangle and therefore also share the side length
BI=AK is false, because we don't know where the intersection point j is on AB, it could split the length into any arbitrary ratio, in case these are two equal sides then it would be true, but it doesn't hold for all other possibilities

so BI=BK is the solution