[A]: The carrier protein cytochrome P450 detoxifies the harmful contents present in cigarette smoke in the lungs.
[R]: This is the sole role of cyt P450.

Options

A. If both A and R are true and R is the correct explanation of A
B. If both A and R are true but R is not the correct explanation of A
C. If A is true and R is false
D. If both A and R are false

Answer

To solve the question regarding the role of cytochrome P450 in detoxifying harmful substances in cigarette smoke, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Cytochrome P450**:
- Cytochrome P450 is a family of enzymes that play a crucial role in the metabolism of various substances in the body, including drugs, steroids, and other xenobiotics.

2. **Role in Detoxification**:
- One of the functions of cytochrome P450 is to detoxify harmful compounds, including those found in cigarette smoke. When cigarette smoke enters the lungs, cytochrome P450 helps in breaking down and detoxifying these harmful substances.

3. **Evaluating Statement [A]**:
- Statement [A] claims that cytochrome P450 detoxifies harmful contents in cigarette smoke in the lungs. This statement is true because it accurately describes one of the functions of cytochrome P450.

4. **Evaluating Statement [R]**:
- Statement [R] claims that detoxification of cigarette smoke is the sole role of cytochrome P450. This statement is false because cytochrome P450 has multiple roles, including the metabolism of drugs and steroids, and is not limited to detoxification of cigarette smoke.

5. **Conclusion**:
- Since [A] is true and [R] is false, the correct answer is that [A] is true and [R] is false.

### Final Answer:
- The correct option is **C**: [A] is true and [R] is false.