**Core Concept**
Cryptogenic organizing pneumonia (COP), previously known as bronchiolitis obliterans organizing pneumonia (BOOP), is a rare inflammatory lung disease characterized by the presence of organizing pneumonia in lung tissue without an identifiable cause. It is often associated with the formation of granulation tissue in the alveoli and bronchioles.

**Why the Correct Answer is Right**
COP is typically characterized by the following features:
- The presence of organizing pneumonia, which involves the formation of granulation tissue in the alveoli and bronchioles.
- A rapid response to corticosteroid therapy.
- No identifiable cause for the disease, such as infection, autoimmune disease, or exposure to toxic substances.
- The presence of a distinctive histological pattern, often referred to as "popcorn" calcifications.

**Why Each Wrong Option is Incorrect**
**Option A:** Not a characteristic of COP, but rather a feature of other lung diseases, such as pulmonary embolism or pneumothorax.
**Option B:** Not a characteristic of COP, but rather a feature of other autoimmune diseases, such as rheumatoid arthritis or lupus.
**Option C:** Not a characteristic of COP, but rather a feature of other lung diseases, such as cystic fibrosis or bronchiectasis.

**Clinical Pearl / High-Yield Fact**
COP is often associated with a good response to corticosteroid therapy, which can lead to rapid improvement in symptoms and lung function. However, relapses can occur, and long-term management may be necessary.

**Correct Answer: A.**