The number of diagonals of a polygon with ‘ n ’ sides is
depending on n (n - 3 ) 2 n
i.e. depending on n^{2} - 3n 2 n
i.e. depending on n^{2} 5 n
i.e. depending on n 5
Hence for a quadrilateral ( n = 4 ) i.e. n < 5 the number of diagonals is less than the number of sides, for a pentagon ( i.e. n = 5 ) the number of diagonal is equal to the number of sides and for ALL other polygons ( with n > 5 ) i.e. from hexagon onwards, the number of sides. Hence can’t say.
Hence D.