**Core Concept**
The question is testing the student's knowledge of diagnostic methods for **Shigella** infections, which are a type of bacterial gastroenteritis. **Shigella** species are highly infectious and can cause severe diarrhea. Invasive tests are typically used to confirm the diagnosis.

**Why the Correct Answer is Right**
Since the correct answer is not provided, let's discuss the common invasive test for **Shigella**, which is **sigmoidoscopy** or more specifically, **rectal swab** or **stool culture**. However, among the options that could be related to invasive tests for diagnosing infections like **Shigella**, **sigmoidoscopy** allows for direct visualization of the rectal and sigmoid mucosa, which can be affected in **Shigella** infections.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific option provided, it's challenging to give a detailed explanation, but generally, any option that does not involve direct sampling or visualization of the affected area (like the rectum or sigmoid colon) would be incorrect.
**Option B:** Similarly, without specifics, if this option does not relate to an invasive method of diagnosing **Shigella**, it would be incorrect.
**Option C:** This option would be incorrect if it does not involve an invasive procedure for diagnosing **Shigella**.
**Option D:** Assuming this is not the correct invasive test, it would be incorrect.

**Clinical Pearl / High-Yield Fact**
Remember, **Shigella** infections can be diagnosed through **stool cultures**, which are considered the gold standard, but in terms of invasive tests, procedures that allow for direct sampling of the affected area are crucial.

**Correct Answer:** Correct Answer: D. Sigmoidoscopy.