Which of the following sugars is present in the nucleotide of $RNA$?

Assertion : Treatment of $D$-glucose with dilute alkali affords an equilibrium mixture consisting of $D$-mannose,$D$-fructose and starting substance $D$-glucose.
Reason : The reaction involves an intermediate in which hybridization of $C_2$ changes from $sp^3$ to $sp^2$.

Complete hydrolysis of cellulose yields .......

Glucose cannot be classified as

Glycosidic linkage between $C_{1}$ of $\alpha$-glucose and $C_{2}$ of $\beta$-fructose is found in.

On prolonged heating with $HI$,glucose gives a compound '$C$',which can be obtained by Wurtz reaction using sodium metal and compound '$D$'. Identify '$D$'.