$D$-Glucose $\overset{OH^{-}}{\longleftrightarrow} A + B$; $A$ and $B$ are

Glucose and mannose are.......

Which of the following statements are true about carbohydrates?
$(i)$ Monosaccharides can be hydrolysed.
$(ii)$ The two monosaccharide units obtained on hydrolysis of a disaccharide can either be same or different.
$(iii)$ Polysaccharides are non-sweet in taste.
$(iv)$ All monosaccharides are not reducing sugars.

The Fischer projection formula of $D-(-)$-fructose is:

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

Maltose contains how many oxygen atoms?