**Core Concept**
Bleomycin toxicity is a well-known side effect of chemotherapy, particularly in patients receiving this medication for cancer treatment. It leads to pulmonary toxicity, manifesting as pneumonitis and potentially resulting in pulmonary fibrosis.

**Why the Correct Answer is Right**
Bleomycin toxicity primarily affects the lungs due to the drug's mechanism of action. It generates free radicals that cause oxidative stress and damage to lung tissue, leading to inflammation and eventual scarring. The enzyme NADPH oxidase is involved in the generation of reactive oxygen species, which contributes to lung damage. The lungs are particularly susceptible to this damage due to their high metabolic rate and exposure to oxygen.

**Why Each Wrong Option is Incorrect**
**Option A:** Liver toxicity is not a primary effect of bleomycin, although it can cause liver enzyme elevations in some cases.
**Option B:** Cardiac toxicity is not a well-documented side effect of bleomycin, although it can cause cardiac arrhythmias in rare instances.
**Option C:** Bone marrow toxicity is not a characteristic feature of bleomycin, although it can cause myelosuppression in some patients.

**Clinical Pearl / High-Yield Fact**
Bleomycin-induced pulmonary toxicity is a dose-dependent side effect, and patients receiving high cumulative doses are at increased risk. Monitoring pulmonary function tests and chest X-rays can help identify early signs of toxicity.

**Correct Answer: C. Lungs.**