It is an acute isosceles triangle, so the vertex angle is smaller than 90.
if the vertex angle is 90, then it is a 45-45-90 triangle, when the longest side (the hypotenuse) is 8, each leg is 8/√2=5.65685
Because the vertex angle needs to be smaller than 90, the two equal side is larger than 5.6568, I'd go with D.
