Which of the following is a pentose sugar?

Identify the glycosidic linkage present in lactose.

The molecular formula of the pentahydroxy acid obtained when glucose is oxidized with $Br_2$ water is:

Which of the following statements is not true about glucose?

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 $sp^2$.

The configurations of the chirality centres in $D$-threose (shown) are