We know that a simple reducing sugar can be divided into 2 groups:

 

The aldose and the ketose

 

A ketose contains 1 group of Ketone group .

 

However , ketone is resistant to oxidation in the organic chemistry context.

 

But ketose is a reducing sugar !!!!

 

 

Can anyone give an idea to this question

Ketones can be oxidized in organic chemistry. They are less succeptible to oxidation than aldehydes, but they can be reduced to secondary alcohols nonetheless.

to act as a reducing agent , it must be oxidised not reduced !!

Ah, you're right, I was thinking of something else.

 

Not all ketoses are reducing sugars. You are absolutely right that ketones are resistant to oxidation because alkyl groups are not good leaving groups. However, 2-ketoses are capable of acting as reducing agents because they are in equilibrium with an aldose form in basic solution (see attached picture).