To find this I would use the pythagorean theorem which is:
a^2 + b^2 = c^2
Since we already know c = hypotenuse, and a side of the shorter sides we can plug them it like this:
11^2 + b^2 = 12^2
121 + b^2 = 144
b^2 = 23
√23 = 4.79
Round:
B. 4.8 would be your answer!
Both a rhombus and a rectangle have diagonals that are perpendicular bisectors, but the ones formed in a square are all congruent, so that is probably the most descriptive one.