According to the properties of parallelogram, two semi-diagonals and one side form a triangle. According to the fact that the sum of the lengths of the two sides of the triangle is greater than the third side, and the difference between the two sides is less than the third side, D satisfying the conditions can be obtained.

According to the shape of the diamond, two diagonals vertically bisect two semi-diagonals and one side of the diamond to form a right triangle. Suppose the diagonals are A and B, then according to Pythagorean Theorem (a/2)? +(b/2)？ =2? Answer? +b？ =4x2？ = 16 Choose one.