Which of the following is CORRECT about amino acid ?

Options

A. It is a compound containing amino `(-NH_2)` and acidic group (–COOH)
B. It is a substituted methane.
C. Based on natural of 'R' group they are of many types
D. All of these

Answer

To solve the question regarding which statement about amino acids is correct, we will analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Amino Acids**:
- Amino acids are organic compounds that serve as the building blocks of proteins. They contain at least one amino group (-NH2) and one carboxyl group (-COOH).

2. **Evaluating Option A**:
- **Statement**: "It is a compound containing an amino and acidic group."
- **Analysis**: This statement is correct because amino acids contain both an amino group and a carboxyl group, which is acidic in nature.

3. **Evaluating Option B**:
- **Statement**: "It is a substituted methane."
- **Analysis**: This statement is also correct. Methane (CH4) has four hydrogen atoms, and in amino acids, the central carbon (alpha carbon) is bonded to four different groups: an amino group, a carboxyl group, a hydrogen atom, and a variable R group. Thus, amino acids can be considered as substituted methanes.

4. **Evaluating Option C**:
- **Statement**: "Based on the nature of the R group, they are of many types."
- **Analysis**: This statement is correct as well. The R group (side chain) varies among different amino acids, leading to a diverse range of amino acids with different properties (e.g., polar, non-polar, acidic, basic).

5. **Conclusion**:
- Since all three statements (A, B, and C) are correct, the answer to the question is:
- **D: All of these.**

### Final Answer:
**D: All of these.**