A square is a shape which has parallel sides (not parallel diagonals), has diagonals that are perpendicular bisector of each other and also its diagonals are congruent.
So according to these properties of square, options A, B and C are wrong and we are left with option D which is the correct one.
This is a 30,60,90 triangle which is know. To be a special triangle which you use a certain rule(shown below) to solve so the hypotenuse or y would be 22 and the the side or x would be approximately 19.05