$\begin{array}{1 1}(a)\;\text{Presence of ketonic group}\\(b)\;\text{Presence of }NH_4OH\text{ in Tollen's reagent}\\(c)\;\text{Rearrangement of fructose into a mixture of glucose fructose and mannose}\\(d)\;\text{Both (b) and (c)}\end{array} $
