In its ring structure, D-glucose has no aldehyde group, it still gives an aldehyde test with Fehling solution ? Explain.

Explanation

### Step-by-Step Solution:

1. **Understanding the Structure of D-Glucose**:
- D-glucose primarily exists in two forms: an open-chain form and a cyclic (ring) form. The cyclic form is more stable and is predominantly found in solution.

2. **Cyclic Structure of D-Glucose**:
- In its cyclic form, D-glucose forms a six-membered ring (pyranose form) through the reaction between the aldehyde group and one of its hydroxyl groups. This results in the formation of a hemiacetal, which does not have a free aldehyde group.

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