**Core Concept**
The question is testing the knowledge of vaccine storage conditions, specifically at Primary Health Care (PHC) level. Vaccines require proper storage to maintain their potency and efficacy. The correct answer will depend on the type of vaccine and its specific storage requirements.

**Why the Correct Answer is Right**
Vaccines can be broadly categorized into two types based on their storage requirements: refrigerated vaccines and lyophilized vaccines. Refrigerated vaccines, such as MMR and DT, require storage between 2°C and 8°C. Lyophilized vaccines, such as BCG and OPV, can be stored at room temperature (20°C to 25°C) for a longer period. However, even lyophilized vaccines require refrigeration once reconstituted.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the storage conditions. Without knowing the type of vaccine, it is difficult to determine the correct storage conditions.
**Option B:** This option is incorrect because it may not be accurate for all vaccines. While some vaccines can be stored at room temperature, others require refrigeration.
**Option C:** This option is incorrect because it may not be accurate for all vaccines. While some vaccines can be stored at room temperature, others require refrigeration.

**Clinical Pearl / High-Yield Fact**
It is essential to check the vaccine package insert or manufacturer's guidelines for specific storage requirements. Additionally, vaccines should be stored in a designated area with a consistent temperature, away from direct sunlight and moisture.

**Correct Answer: C. Room temperature (20°C to 25°C).