Okay, let's tackle this question. The user is asking about a helminth whose eggs can be concentrated using a saturated salt solution. First, I need to recall the methods used for concentrating parasite eggs in stool samples. Saturated salt solution is a flotation technique, right? It's used because the eggs of certain parasites are less dense than the solution and float to the top.

Now, which helminths have eggs that float? I remember that hookworm eggs are a common one. Their eggs are thin-shelled and have a characteristic shape. Also, the salt solution has a specific gravity higher than the eggs, so they float. But wait, maybe other helminths like Ascaris or Trichuris? Wait, Ascaris eggs are more likely to be seen with other methods, maybe direct wet mount. Trichuris eggs are barrel-shaped and might not float as easily.

Wait, the key here is the concentration method. Flotation with saturated sodium chloride is specifically used for lighter eggs. Hookworm eggs are definitely a classic example. Another possibility is Strongyloides, but I think their eggs might be more elongated and might not float as well. Maybe also pinworms? No, pinworm eggs are usually detected using the cellophane tape test.

So the correct answer should be hookworm. The other options are probably other helminths like Ascaris, Trichuris, or maybe Schistosoma, which have eggs that don't float. Let me confirm. Hookworm eggs are indeed concentrated using this method because they float. So the correct answer is hookworm. The distractors would be other helminths whose eggs don't float with this method. Need to make sure each incorrect option is explained properly.

**Core Concept**
This question tests knowledge of parasitological diagnostic techniques, specifically the **saturated salt solution flotation method**, which is used to concentrate and detect **helminth eggs** with lower specific gravity than the solution (e.g., hookworm, Trichuris, and some protozoan cysts).

**Why the Correct Answer is Right**
The **saturated sodium chloride solution** (specific gravity ~1.2) causes lighter eggs (e.g., **hookworm eggs**) to float to the surface when mixed with stool. Hookworm eggs (Ancylostoma duodenale/Necator americanus) are thin-walled, oval, and contain 4–8 refractile ova, making them ideal for this method. The flotation technique enhances detection by concentrating eggs, which are otherwise sparse in stool samples.

**Why Each Wrong Option is Incorrect**
**Option A:** *Ascaris lumbricoides* eggs have thick, pitted shells and higher density; they do not float in salt solution.
**Option B:** *Trichuris trichiura* (whipworm) eggs are barrel-shaped and heavy, requiring formalin-ether sedimentation instead.
**Option C:** *Schistosoma* eggs have opercula and are best detected via direct smear or sedimentation, not flotation.

**Clinical Pearl / High-Yield Fact**
Remember: **"Hookworms float, whipworms sink."** Use salt flotation for hookworms; use formalin-ether sedimentation for heavier eggs like *Trichuris* or

✓ Correct Answer: D. Ancylostoma duodenale