Which of the following sugar is found in milk?

Identify the enzyme $X$ in the following reaction

$\mathrm{H}_2 \mathrm{O}_2(\mathrm{aq}) \xrightarrow{x} \mathrm{H}_2 \mathrm{O}(l)+\frac{1}{2} \mathrm{O}_2(g)$

Which reagent among the following is used to confirm presence of aldehydic carbonyl group in glucose?

Which carbon atoms of $\alpha-D$ glucopyranose and $\beta$-D-fructofuranose respectively are linked together to form glycosidic linkage in sucrose?