Okay, let's tackle this question. The user is asking about the class of amino acids that contains only non-essential ones. First, I need to recall the classification of amino acids. There are 20 standard amino acids, which are divided into essential and non-essential.

Essential amino acids are those the body can't synthesize, so they must come from the diet. Non-essential are those the body can make on its own. Wait, but there's also a category called conditionally essential, which are non-essential under normal conditions but may need to be supplemented in certain cases like illness or stress. But the question is about the class with only non-essential, so I should focus on that.

The options aren't provided, so I need to infer based on common classifications. The classes are often grouped by structure or function. For example, there's a group of sulfur-containing amino acids like methionine and cysteine. Methionine is essential, so if cysteine is non-essential, that group would contain a mix. Another group is the acidic amino acids: aspartic acid and glutamic acid, both non-essential. That might be the correct answer.

Another possibility is the basic amino acids (lysine, arginine, histidine). Lysine and arginine are essential, so that group would have essential ones. The branched-chain amino acids include leucine, isoleucine, valine—all essential. So the correct class would be acidic amino acids since both aspartic acid and glutamic acid are non-essential.

Wait, but sometimes histidine is considered conditionally essential. However, the question is about only non-essential. So the acidic group (aspartic and glutamic) is the right answer. The options might be labeled as A to D with different groups. The correct answer would be the acidic amino acids class.

**Core Concept**
Non-essential amino acids are synthesized by the human body and do not require dietary intake. The classification of amino acids into groups (e.g., acidic, basic, neutral) helps identify their biochemical roles and metabolic pathways.

**Why the Correct Answer is Right**
The **acidic amino acids** class includes **aspartic acid** and **glutamic acid**, both of which are non-essential. These amino acids are synthesized via the citric acid cycle and transamination pathways. Their carboxyl groups are deprotonated at physiological pH, giving them a negative charge. This group does not include any essential amino acids, making it the correct answer.

**Why Each Wrong Option is Incorrect**
**Option A:** *Sulfur-containing amino acids* include **methionine** (essential) and **cysteine** (non-essential), so this class contains both.
**Option B:** *Branched-chain amino acids* (valine, leucine, isoleucine) are all **essential**, not non-essential.
**Option C:** *Basic amino acids* (lysine, arginine, histidine) include **lysine and arginine** (essential) and **histidine** (conditionally essential).

**Clinical Pearl / High-Yield Fact**
Remember the **"Acidic Aces": Aspartic and Glutamic**—both are non-essential and part of the acidic group. This

✓ Correct Answer: A. Acidic