**Question:** The eosinophil count in the peripheral blood smear is increased in:

***Core Concept:***
Eosinophils are a type of white blood cell that plays a crucial role in the immune system, particularly in defending against parasitic infections. They are part of the innate immune system and are involved in the response to helminthic (worm) infections. Eosinophilia refers to an increase in the number of eosinophils in the peripheral blood smear.

***Why the Correct Answer is Right:***
The correct answer is C, "Infections (parasitic, bacterial, and viral)." An increase in eosinophil count is a common response to parasitic infections, particularly those involving helminths (worms). Eosinophils are mobilized from the bone marrow to the peripheral blood to fight against parasites.

***Why Each Wrong Option is Incorrect:***
A) "Immune disorders" is incorrect because while eosinophilia can occur in certain immune disorders, the correct answer is more specific to infections.
B) "Hypersensitivity reactions" is incorrect because, while eosinophilia may occur in hypersensitivity reactions, the answer is more specific to infections.
D) "Neoplastic disorders" is incorrect because while eosinophilia can be seen in certain neoplastic disorders, the answer is more specific to infections.

***Clinical Pearl:***
Eosinophilia can be a useful diagnostic clue in clinical practice, especially in endemic areas where parasitic infections are common. A high eosinophil count can point towards a parasitic infection, allowing for targeted investigations and treatment.

***Correct Answer:***
C) "Infections (parasitic, bacterial, and viral)"

**Answer Explanation:**
Eosinophilia is a reaction to the presence of parasites, bacteria, or viruses, which are the primary cause of infections in this context. The increase in eosinophil count helps the immune system to combat these pathogens, making infections the most appropriate answer choice.