Question Analysis: Assertion-Reason type question.

Step 1 (Analysis of Assertion): [0.5 Mark]
The reaction of glucose with bromine water ($Br_2$ water) is a mild oxidation process. Bromine water acts as a mild oxidizing agent that oxidizes the aldehydic group ($-CHO$) of glucose to a carboxylic acid group ($-COOH$), forming gluconic acid. The reaction is represented as:

Thus, the Assertion (A) is True.

Step 2 (Analysis of Reason): [0.5 Mark]
The open-chain structure of glucose is $CHO-(CHOH)_4-CH_2OH$. It contains a carbonyl group in the form of an aldehyde ($-CHO$) at the $C_1$ position. The statement that the carbonyl group is absent is factually incorrect. Therefore, the Reason (R) is False.

Step 3 (Final Concluded Answer): [1 Mark]
Since Assertion (A) is True but Reason (R) is False, the correct option is:

Assertion (A) is true but Reason (R) is false.

💡 EL10 Concept Insight: Think of bromine water like a gentle filter that only changes the "head" of the glucose molecule into an acid, but the reason is wrong because glucose definitely has a carbonyl group—it's the very part that gets turned into the acid!