**Core Concept**
Loeffler's syndrome is a type of pulmonary eosinophilia characterized by the accumulation of eosinophils in the lung parenchyma, leading to transient pulmonary infiltrates on imaging. This condition is often associated with parasitic infections, allergic reactions, and other hypersensitivity reactions.

**Why the Correct Answer is Right**
The correct answer involves identifying conditions that are not typically associated with Loeffler's syndrome. This requires an understanding of the underlying pathophysiology, which involves an abnormal immune response to foreign substances or allergens. In Loeffler's syndrome, the immune response is characterized by an increase in eosinophils, which are a type of white blood cell involved in fighting parasites and other foreign substances.

**Why Each Wrong Option is Incorrect**
**Option A:** Ascaris lumbricoides - While Ascaris infections can cause pulmonary symptoms, they are more commonly associated with Loeffler's syndrome, so this option is incorrect.
**Option B:** Histoplasmosis - This fungal infection is not typically associated with Loeffler's syndrome, which is more commonly linked to parasitic infections and allergic reactions.
**Option C:** Coccidioidomycosis - This fungal infection is caused by Coccidioides immitis and can cause pulmonary symptoms, but it is not typically associated with Loeffler's syndrome.
**Option D:** Echinococcosis - This parasitic infection is caused by the Echinococcus tapeworm and can cause pulmonary symptoms, but it is not typically associated with Loeffler's syndrome.

**Clinical Pearl / High-Yield Fact**
Loeffler's syndrome is often associated with parasitic infections, particularly those caused by Ascaris lumbricoides, Strongyloides stercoralis, and Ancylostoma duodenale. These infections can cause pulmonary symptoms and eosinophilia, which are characteristic of Loeffler's syndrome.

**Correct Answer:** B. Histoplasmosis.