**Core Concept**
The question is testing the student's knowledge of a diagnostic test used in dermatology to identify infectious cysts. This test involves an intradermal injection of a sterilized fluid from the cyst, which causes an immune response.

**Why the Correct Answer is Right**
The correct answer is a diagnostic test that involves the intradermal injection of a cyst fluid to elicit an immune response. This test is used to diagnose conditions such as pilonidal cysts, epidermoid cysts, and dermoid cysts. The injected fluid contains antigens that stimulate an immune response, leading to the formation of a nodule or papule at the injection site. This reaction is a sign that the individual has developed an immune response to the cyst fluid, indicating that the cyst is infectious.

**Why Each Wrong Option is Incorrect**
**Option A:** This is not a valid diagnostic test. While it may sound plausible, it is not a recognized method for diagnosing infectious cysts.
**Option B:** This is not the correct answer. While it may be a related concept, it is not the specific test described in the question.
**Option C:** This is not a diagnostic test, but rather a treatment option for certain conditions.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the diagnosis of infectious cysts often relies on a combination of clinical evaluation, imaging studies, and laboratory tests. The intradermal injection test is a useful tool in the diagnostic process, but it should be used in conjunction with other diagnostic methods to confirm the diagnosis.

**Correct Answer: C. Mantoux test is incorrect. The correct answer is not listed. A possible answer is Cysticercosis reaction test.