**Core Concept**
The metabolism of xenobiotics refers to the process by which the body breaks down and eliminates foreign substances, such as drugs and environmental pollutants. This process involves a series of enzyme-catalyzed reactions that transform the xenobiotic into more water-soluble compounds that can be easily excreted.

**Why the Correct Answer is Right**
Xenobiotics, including endogenous compounds like bilirubin and steroid hormones, undergo phase I and phase II metabolism. Phase I reactions, catalyzed by cytochrome P450 enzymes, involve oxidation, reduction, or hydrolysis to create a more reactive intermediate. Phase II reactions, catalyzed by conjugation enzymes, involve the addition of a molecule such as glucuronic acid, sulfate, or acetyl group to the intermediate, making it more water-soluble and easier to excrete.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the metabolic pathway or enzyme involved. While it's true that some compounds are metabolized like xenobiotics, this option is too vague to be a correct answer.
**Option B:** This option is incorrect because it does not accurately describe the metabolism of xenobiotics. While some compounds may be metabolized by specific enzymes, this option does not address the broader process of xenobiotic metabolism.
**Option C:** This option is incorrect because it is too general and does not specifically refer to the metabolism of xenobiotics. Many compounds are metabolized in the liver, but this option does not capture the unique characteristics of xenobiotic metabolism.

**Clinical Pearl / High-Yield Fact**
Xenobiotic metabolism is a critical process that helps protect the body from the toxic effects of foreign substances. Understanding the enzymes and pathways involved in xenobiotic metabolism is essential for predicting drug interactions and avoiding adverse reactions.

**Correct Answer:** A.