Which of the following monosaccharides is a pentose?

Which of the following reagents cannot distinguish between glucose and fructose?

$\alpha - D - (+) -$ glucose and $\beta - D - (+) -$ glucose are:

$A$ sugar '$X$' dehydrates very slowly under acidic conditions to give furfural,which on further reaction with resorcinol gives a coloured product after some time. Sugar '$X$' is

Glucose cannot be classified as which of the following?

Which one of the following is the structure of lactose?