**Core Concept**
The general test for detection of carbohydrates involves a biochemical reaction that produces a visible product, indicating the presence of carbohydrate molecules. This reaction is based on the oxidation of carbohydrates by an enzyme, resulting in the formation of a colored compound. The most commonly used test for detecting carbohydrates is the Benedict's test.

**Why the Correct Answer is Right**
The Benedict's test is a widely used method for detecting the presence of reducing sugars in a sample. The test involves the addition of Benedict's reagent, a alkaline copper sulfate solution, to the sample. The reducing sugars present in the sample react with the copper ions in the reagent, resulting in the formation of a brick-red precipitate of copper oxide. This visible precipitate indicates the positive result of the test. The reaction occurs due to the oxidation of the reducing sugars by the copper ions, resulting in the loss of electrons and the formation of the colored compound.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because the Benedict's test is specific for reducing sugars and does not detect non-reducing sugars.
**Option B:** This is incorrect because the Fehling's test is another test for detecting reducing sugars, but it is not the general test for detection of carbohydrates.
**Option C:** This is incorrect because the Molisch's test is a general test for detecting carbohydrates, but it involves the addition of α-naphthol and sulfuric acid to the sample, resulting in the formation of a purple color.

**Clinical Pearl / High-Yield Fact**
The Benedict's test is a rapid and sensitive method for detecting the presence of reducing sugars in a sample, and it is commonly used in clinical settings to diagnose conditions such as diabetes mellitus.

**Correct Answer: D.