## Core Concept
The core concept here revolves around the prevention of varicella (chickenpox) transmission, particularly to a pregnant woman, who is at higher risk for complications. Varicella is caused by the varicella-zoster virus, and its transmission can be prevented by ensuring the individual is no longer contagious.

## Why the Correct Answer is Right
The correct answer hinges on understanding the contagious period of varicella. A person with varicella is contagious from 1-2 days before the onset of the rash until all the lesions have crusted over, usually around 5-7 days after the onset of the rash. The virus spreads through direct contact with rash lesions or through airborne transmission. For a child with varicella to safely meet a pregnant aunt, the child must no longer be contagious.

## Why Each Wrong Option is Incorrect
- **Option A:** This option suggests an immediate meeting, which is incorrect because the child is still contagious at this point.
- **Option B:** This option might still be within the contagious period, depending on when the rash appeared and when the lesions crusted over.
- **Option D:** This option suggests a longer wait than necessary based on standard guidelines for varicella contagiousness.

## Clinical Pearl / High-Yield Fact
A key point to remember is that for varicella, isolation typically continues until all lesions have crusted over, which is often around 5-7 days after the onset of the rash, but this can vary slightly. Pregnant women are at increased risk for severe varicella, making prevention of transmission crucial.

## Correct Answer Line
**Correct Answer: C.**