The minimum number of carbon atoms that should be present in a carbohydrate is:

Options

A. 2
B. 3
C. 4
D. 6

Explanation

To solve the question regarding the minimum number of carbon atoms that should be present in a carbohydrate, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Carbohydrates**: Carbohydrates are biomolecules that consist of carbon (C), hydrogen (H), and oxygen (O) atoms. They can be classified into monosaccharides, disaccharides, oligosaccharides, and polysaccharides.

2. **Identify Monosaccharides**: The simplest form of carbohydrates is monosaccharides. These are the building blocks of more complex carbohydrates.

3. **Know the General Formula**: The general formula for monosaccharides is \( C_n(H_2O)_n \), where \( n \) is the number of carbon atoms. This can also be represented as \( C_nH_{2n}O_n \).

4. **Determine the Range of n**: For monosaccharides, the value of \( n \) can vary from 3 to 7. This means that the smallest monosaccharide must have at least 3 carbon atoms.

5. **Identify the Simplest Monosaccharides**: The simplest carbohydrate with 3 carbon atoms is glyceraldehyde, which has the molecular formula \( C_3H_6O_3 \). Another example is dihydroxyacetone, which also has 3 carbon atoms.

6. **Conclusion**: Therefore, the minimum number of carbon atoms that should be present in a carbohydrate is 3.

### Final Answer:
The minimum number of carbon atoms that should be present in a carbohydrate is **3**.