Correct Answer - D
`DU=0`
`therefore` (1)`C-undersetunderset(C)(|)oversetoverset(C)(|)C-undersetunderset(C)(|)C-C-C` , (2)`C-undersetunderset(C)(|)(C)-undersetunderset(C)(|)(C)-undersetunderset(C)(|)(C)-C` (3)`C-C-undersetunderset(C)(|)oversetoverset(C)(|)(C)-undersetunderset(C)(|)(C)-C` , (4)`C-undersetunderset(C)(|)oversetoverset(C)(|)(C)-C-undersetunderset(C)(|)(C)-C`