**Core Concept**
Measles vaccine, a live attenuated vaccine, requires proper storage to maintain its potency and effectiveness. The storage temperature is critical to prevent degradation of the vaccine's live attenuated virus. The World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) provide guidelines for vaccine storage.

**Why the Correct Answer is Right**
The measles vaccine is typically stored at a refrigerator temperature of 2-8°C (36-46°F). This temperature range allows the live attenuated virus to remain viable and effective, ensuring the vaccine's potency and efficacy. The vaccine should not be frozen, as this can cause damage to the virus, rendering it ineffective. Additionally, temperatures above 25°C (77°F) can also compromise the vaccine's potency.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is likely incorrect, as vaccines are typically stored at refrigerator temperatures, not room temperature.
**Option B:** This option is incorrect, as temperatures above 25°C (77°F) can compromise the vaccine's potency.
**Option C:** This option is incorrect, as freezing temperatures can damage the live attenuated virus, rendering it ineffective.

**Clinical Pearl / High-Yield Fact**
Remember, vaccines are sensitive to temperature, and improper storage can lead to reduced potency and efficacy. Always follow the manufacturer's guidelines and storage recommendations for vaccines.

**Correct Answer: D. 2-8°C (36-46°F)**