Which of the following substances is found in abundance in nature?

With which reagent does glucose react to form a crystalline osazone derivative?

Which of the following is a polysaccharide?

The functional groups involved in the conversion of glucose to gluconic acid and gluconic acid to saccharic acid respectively are

Compound $A$,$C_5H_{10}O_5$,gives a tetraacetate with $Ac_2O$ and oxidation of $A$ with $Br_2-H_2O$ gives an acid,$C_5H_{10}O_6$. Reduction of $A$ with $HI$ gives isopentane. The possible structure of $A$ is:

Which of the following pairs is a $C_2$-epimer?