The correct option is C Both (a) and (b)
Despite having aldehyde group, glucose does not give Schiff’s test & it does not form the hydrogen sulphite (bisulphite) addition product with NaHSO3. Schiff’s reagent is a dilute solution of rosaniline hydrochloride whose pink colour has been discharged by passing SO2. Aldehyde restores pink colour when treated with Schiff’s reagent (Magenta solution in H2SO3). The pentaacetate of glucose does not react with hydroxylamine indicating the absence of free –CHO group. These behaviour couldn’t be explained by open chain structure. It was proposed that one of –OH group may add to –CHO group to form a cyclic structure. Hence, the correct answer is option (c).