Essential amino acids include

Options

A. leucine
B. valine
C. tryptophan
D. all of these

Explanation

**Step-by-Step Solution:**

1. **Understanding Amino Acids**: Amino acids are organic compounds that serve as the building blocks of proteins. They play crucial roles in various biological processes.

2. **Defining Essential Amino Acids**: Essential amino acids are those that cannot be synthesized by the body. Therefore, they must be obtained through diet.

3. **Listing Essential Amino Acids**: There are nine essential amino acids that the human body cannot produce. These include:
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine

4. **Evaluating the Options**: The question provides several options:
- Option 1: Leucine
- Option 2: Valine
- Option 3: Tryptophan
- Option 4: All of these

5. **Identifying Correct Options**:
- Leucine is an essential amino acid.
- Valine is also an essential amino acid.
- Tryptophan is another essential amino acid.

6. **Conclusion**: Since all three options (Leucine, Valine, and Tryptophan) are essential amino acids, the correct answer is:
- **Option 4: All of these**.

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