Which of the following is a reducing sugar?

Milk contains which of the following disaccharides?

$L$-isomer of tetrose $X$ $(C_4H_8O_4)$ gives positive Schiff's test and has two chiral carbons. On acetylation,$X$ yields triacetate. $X$ also undergoes the following reactions:
$X$ $\xrightarrow{HNO_3} A$ $\xrightarrow{NaBH_4} \underset{\text{Chiral compound}}{B}$
$X$ is $.......$.

Starch and cellulose are compounds made up of many ...... units.

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

Observe the following statements.
$I$. Sucrose has glycosidic linkage.
$II$. Cellulose is present in both plants and animals.
$III$. Lactose contains $D$-galactose and $D$-glucose units.
Which of the following statements are correct?