A square tablecloth with side length a is placed on a round table with diameter B (a > b). If the maximum length of the four corners of the tablecloth is equal, the maximum length is () A. 2a−bB. 2a−b2C. 22a−b2D. 22a−b

A square tablecloth with side length a is placed on a round table with diameter B (a > b). If the maximum length of the four corners of the tablecloth is equal, the maximum length is () A. 2a−bB. 2a−b2C. 22a−b2D. 22a−b

The diagonal line of the square is 2a, the diameter of the round table is B, and the maximum length of the tablecloth is 12 (2a-b) = 22a − B2