**Core Concept**
The BCG (Bacillus Calmette-Guérin) vaccine, a live attenuated vaccine, is used to protect against tuberculosis. Proper dilution of the BCG vaccine is crucial to ensure its potency and safety.

**Why the Correct Answer is Right**
The BCG vaccine is typically reconstituted with normal saline to create a suitable dilution for intradermal administration. Normal saline provides an isotonic environment that helps to preserve the viability of the attenuated Mycobacterium bovis organisms. This is essential for an effective immune response and to minimize the risk of adverse reactions.

**Why Each Wrong Option is Incorrect**
**Option A:** Distilled water is not suitable for reconstituting the BCG vaccine because it lacks essential ions and electrolytes, which can lead to osmotic shock and inactivate the organisms.
**Option C:** Dextrose solution is not used to dilute the BCG vaccine as it can create an environment that fosters the growth of contaminants, compromising the vaccine's efficacy and safety.
**Option D:** Ringer-lactate solution, while isotonic, is not the preferred diluent for the BCG vaccine. Normal saline is the standard choice due to its simplicity and lack of potential contaminants.

**Clinical Pearl / High-Yield Fact**
When handling the BCG vaccine, it's essential to follow proper reconstitution and storage procedures to maintain its potency and ensure safe administration.

**✓ Correct Answer: B. Normal saline**