The amino acids we cannot synthesize are called ................because we ..........

Options

A. unnecessary, therefore do not need them
B. limiting, must include them in our diet
C. anabolic, must use alternative amino acids
D. essential, must include them in our diet

Explanation

**Step-by-Step Solution:**

1. **Understanding Amino Acids**: There are 20 known amino acids that are essential for various bodily functions. These amino acids can be categorized into two groups: essential amino acids and non-essential amino acids.

2. **Defining Essential Amino Acids**: Essential amino acids are those that our body cannot synthesize on its own. This means that they are not produced naturally within our body.

3. **Defining Non-Essential Amino Acids**: Non-essential amino acids, on the other hand, can be synthesized by the body. This means that our body is capable of producing these amino acids without needing to obtain them from our diet.

4. **Conclusion**: Since the question specifically asks about the amino acids that we cannot synthesize, the correct term to fill in the blank is "essential." Therefore, the complete answer is: "The amino acids we cannot synthesize are called **essential** because we **must obtain them from our diet**."

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