Three identical rings of radius 1 unit are stacked as shown in the figure. The length x is

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Solution : 
The three identical rings have a radius of 1 unit
The distance between the center of the top ring and the ground includes:
The radius of the bottom rings (1 unit)
The vertical distance between the center of the top ring and the line joining the centers of the bottom two rings
The centers of the three rings form an equilateral triangle, where each side equals 2 (the diameter of a ring)

 $$h = \frac{\sqrt{3}}{2} \times 2 = \sqrt{3}.$$
This is the vertical height of the equilateral triangle. The center of the top ring is at this height above the centers of the bottom two rings.
$$x = 1 + \sqrt{3} + 1 = 2 + \sqrt{3}$$
Thus the correct answer is option (A) $$2 + \sqrt{3}$$​​