**Core Concept**
The metabolism of xenobiotics involves the conversion of foreign compounds into more water-soluble substances that can be easily excreted from the body. This process is primarily carried out by enzymes within the liver.

**Why the Correct Answer is Right**
The correct answer is **B. Cytochrome p450**, which refers to a family of enzymes that play a crucial role in the metabolism of xenobiotics. Specifically, cytochrome P450 enzymes catalyze the oxidation of lipophilic xenobiotics, making them more hydrophilic and facilitating their excretion. This process involves the addition of oxygen to the xenobiotic molecule, resulting in the formation of a more water-soluble metabolite. The cytochrome P450 system is responsible for metabolizing a wide range of substances, including drugs, environmental pollutants, and other foreign compounds.

**Why Each Wrong Option is Incorrect**
**Option A:** Cytochrome is a broad term that refers to a group of heme-containing proteins involved in electron transport and other cellular processes. While cytochrome P450 is a type of cytochrome, the term "cytochrome" alone is too general to be correct.

**Option C:** Cytochrome C is a specific type of cytochrome that plays a key role in the electron transport chain during cellular respiration. It is not directly involved in the metabolism of xenobiotics.

**Option D:** Cytochrome A is not a commonly recognized term in the context of xenobiotic metabolism. While cytochrome P450 enzymes are often referred to by their specific isoforms (e.g., CYP1A2, CYP2D6), "cytochrome A" is not a valid designation for any known enzyme involved in xenobiotic metabolism.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the cytochrome P450 system is inducible, meaning that the expression and activity of these enzymes can be increased or decreased in response to various factors, such as diet, drugs, and environmental pollutants. This has important implications for the metabolism and toxicity of xenobiotics in the body.

**✓ Correct Answer: B. Cytochrome p450**