Which of the following has `X-O-X` linkage?
`{:((a),H_(2)S_(2)O_(6),(b),H_(6)P_(6)O_(18)),((c),P_(4)O_(10),(d),Na_(2)B_(4)O_(5)(OH)_(4)*8H_(2)O),((e),Na[B_(5)O_(6)(OH)_(4)],(f),Na_(2)S_(2)O_(8)),((g),K_(2)S_(2)O_(7),(h),K_(2)Cr_(2)O_(7)),((i),Na_(4)P_(2)O_(8),(h),K_(2)Cr_(2)O_(7)),((i),Na_(4)P_(2)O_(8),(j),Na_(2)B_(2)O(OH)_(6)):}`
(k) Hypophosphoric acid (tribasic)

Answer

8

Explanation

b, c, d, e, g, h, j, k