**Core Concept**
The question is testing the understanding of contact tracing and public health measures for COVID-19. Contact tracing involves identifying individuals who have come into close contact with an infected person and monitoring them for symptoms of the disease.

**Why the Correct Answer is Right**
Close contacts of a COVID-19 patient are typically defined as individuals who have spent at least 15 minutes within 6 feet (1.8 meters) of the infected person. They are usually advised to self-isolate for 14 days from the last exposure to the infected person. This allows for early detection and isolation of potential cases, thereby preventing further transmission of the virus.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the correct duration of self-isolation for close contacts of COVID-19 patients.
**Option B:** This option is incorrect because it does not mention the specific distance or duration of exposure required for contact tracing.
**Option C:** This option is incorrect because it does not provide the correct duration of self-isolation for close contacts of COVID-19 patients.

**Clinical Pearl / High-Yield Fact**
It's essential for healthcare professionals to follow standard protocols for contact tracing, including self-isolation for 14 days from the last exposure to the infected person, to prevent further transmission of COVID-19.

**Correct Answer: D. 14 days.**