**Core Concept**
The question is testing the ability to identify a periapical radiolucency or radio-opacity in the context of a non-vital asymptomatic tooth with a deep carious lesion. This is related to the principles of endodontic pathology and the interpretation of radiographic findings.

**Why the Correct Answer is Right**
The presence of radio-opacity at the apex of a non-vital tooth is suggestive of an endodontic periapical lesion, which can be caused by the root canal system's response to infection or trauma. The radio-opacity at the apex may be due to the deposition of calcified tissue or the presence of a granuloma or cyst. This is a common radiographic finding in teeth with necrotic pulp or a deep carious lesion that has not been treated.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a periapical radiolucency would be more characteristic of a non-vital tooth with a deep carious lesion, rather than radio-opacity.

**Option B:** This option is incorrect because a periapical radiolucency would be more characteristic of a non-vital tooth with a deep carious lesion, rather than radio-opacity.

**Option D:** This option is incorrect because a periapical radiolucency would be more characteristic of a non-vital tooth with a deep carious lesion, rather than radio-opacity.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the presence of radio-opacity at the apex of a non-vital tooth does not necessarily indicate a successful root canal treatment. A thorough clinical and radiographic evaluation is necessary to determine the extent of the lesion and the need for further treatment.

**Correct Answer:** C.