**Core Concept**
The question is testing the ability to distinguish between different types of parasitic infections based on the size of the eggs and their clinical presentation. The correct answer requires knowledge of the typical egg sizes and clinical manifestations of various intestinal parasites.

**Why the Correct Answer is Right**
The eggs of Ascaris lumbricoides, which are typically 70-100 µm in size, are often associated with abdominal cramps and diarrhea. However, the eggs are usually not directly seen in the stool, as they are ingested and then hatch in the small intestine, releasing larvae that migrate to the lungs and then back to the intestines. The clinical presentation of Ascaris infection is more likely to involve respiratory symptoms, such as coughing and wheezing, due to the migration of larvae through the lungs.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because hookworm eggs are usually smaller, around 50-60 µm in size, and are not typically associated with abdominal cramps and loose stool.
* **Option B:** This option is incorrect because the eggs of Taenia saginata, also known as the beef tapeworm, are usually larger, around 100-120 µm in size, and are not typically associated with abdominal cramps and loose stool.
* **Option C:** This option is incorrect because the eggs of Trichuris trichiura, also known as the whipworm, are usually smaller, around 60-70 µm in size, and are not typically associated with abdominal cramps and loose stool.

**Clinical Pearl / High-Yield Fact**
When considering the diagnosis of intestinal parasites, it's essential to remember that the size and shape of the eggs, as well as the clinical presentation, can help narrow down the differential diagnosis.

**Correct Answer: D.**