**Core Concept**
Neutrophil extracellular traps (NETs) are a network of extracellular fibers that trap and kill pathogens, including parasites. This process involves the release of histones and granular proteins from neutrophils, which then form a complex with DNA to create a sticky web-like structure.

**Why the Correct Answer is Right**
The correct answer is **A. Neutrophils and Eosinophils**. Neutrophils are the primary cells involved in NET formation, releasing histones and granular proteins, such as myeloperoxidase, to create the NET structure. Eosinophils also play a role in this process by releasing major basic protein (MBP) and eosinophil cationic protein (ECP), which help to stabilize and consolidate the NET. This synergistic effect between neutrophils and eosinophils enhances the ability of NETs to trap and kill parasites.

**Why Each Wrong Option is Incorrect**
**Option B:** Monocytes are not directly involved in NET formation, although they may contribute to the phagocytosis of pathogens trapped by NETs. Their role is more supportive rather than primary.

**Option C:** While eosinophils do play a role in the process, monocytes are not essential for NET formation. This combination is not as effective as the synergistic effect between neutrophils and eosinophils.

**Option D:** NK cells are not directly involved in NET formation or the trapping of parasites. They play a role in innate immunity, primarily through cell-mediated cytotoxicity.

**Clinical Pearl / High-Yield Fact**
Remember that NETs are a key mechanism of innate immunity against pathogens, including parasites. The combination of neutrophils and eosinophils in this process highlights the importance of a coordinated immune response in fighting infections.

**✓ Correct Answer: A. Neutrophils and Eosinophils**