**Core Concept**
Curschmann's spirals are a microscopic finding in the sputum of patients with asthma, representing a mixture of mucus and epithelial cells that have been extruded from the airways. They are a hallmark of chronic bronchitis and asthma, and their presence can indicate ongoing airway inflammation.

**Why the Correct Answer is Right**
Curschmann's spirals are formed when mucus and epithelial cells from the airway lining are expelled along with the bronchial secretions. This process is a result of the chronic inflammation and airway remodeling seen in asthma and chronic bronchitis. The spirals are thought to be a result of the twisting of the airway mucosa as the cells are extruded.

**Why Each Wrong Option is Incorrect**
**Option A:** Not relevant, as Curschmann's spirals are a specific finding in respiratory disease.
**Option B:** While eosinophils are involved in asthma pathophysiology, they are not directly related to the formation of Curschmann's spirals.
**Option C:** This is a distractor, as Curschmann's spirals are not seen in normal sputum.

**Clinical Pearl / High-Yield Fact**
Curschmann's spirals are a useful diagnostic clue in patients with chronic cough or wheezing, and their presence can support a diagnosis of asthma or chronic bronchitis.

**Correct Answer: C. Curschmann's spirals are seen in asthma.**