The two forms of $D$-Glucopyranose are called

The number of possible stereoisomers for glucose is .......... .

At which carbon atom do $\alpha-$ and $\beta-$ glucose differ in the configuration of the $-OH$ group?

Four carbohydrates: glucose,lactose,sucrose,and starch are present. Different tests are carried out with these $4$ carbohydrates separately. The following observations are made:
$(a)$ Heated: It is charred.
$(b)$ $I_2$ solution: No violet colour.
$(c)$ Fehling solution: Reddish brown precipitate is observed.
$(d)$ It does not reduce copper$(II)$ acetate to $Cu_2O$. No red precipitate is observed in $5 \ min$.
Which carbohydrate satisfies all the above observations?

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

Which carbohydrate is an essential constituent of plant cell walls?