Carcinogen present in tobacco smoke is nicotine/benzpyrene.

Explanation

To determine the correct answer to the question about the carcinogen present in tobacco smoke, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Carcinogen**:
- A carcinogen is any substance that promotes the formation of cancer. This can include chemicals, viruses, or radiation.

2. **Identify the Components of Tobacco Smoke**:
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