$D$-Glucose and $L$-Glucose are

What is the number of $-OH$ groups present in one molecule of ribose?

$\alpha-D$-Glucopyranose and $\beta-D$-Glucopyranose are:

Considering the facts that
$I$. sucrose forms glycosidic linkage between $C_1$ of glucose and $C_2$ of fructose,while
$II$. lactose forms glycosidic linkage between $C_1$ of galactose and $C_4$ of glucose.
Choose the correct statement.

How many products are produced respectively when optically pure glucose and fructose are reduced one by one by $NaBH_4$?

The letter '$D$' in carbohydrates represents