**Core Concept**
The reflection factor is a measure used in building design and ventilation systems to optimize the exchange of air between the indoor and outdoor environments. It is essential in preventing the spread of airborne diseases and maintaining indoor air quality. The recommended reflection factors vary based on different surfaces and components within a building.

**Why the Correct Answer is Right**
Roofs typically have a lower reflection factor compared to other surfaces due to their design and material composition. A reflection factor of 40% for roofs is generally considered too high, as it would lead to excessive heat gain and decreased ventilation efficiency. In contrast, ceilings, walls, and furniture have higher reflection factors, which are more suitable for promoting air exchange and maintaining indoor air quality.

**Why Each Wrong Option is Incorrect**
**Option A:** Ceilings with a reflection factor of 80% are actually considered high, as they can effectively promote air exchange and reduce stagnation.
**Option C:** Walls with a reflection factor of 50 to 60% are within the recommended range, as they can facilitate air movement while minimizing heat gain.
**Option D:** Furniture with a reflection factor of 30 to 40% is also within the acceptable range, as it can help to distribute and dissipate air within a room.

**Clinical Pearl / High-Yield Fact**
When designing or evaluating ventilation systems, it is essential to consider the reflection factors of various surfaces to optimize air exchange and prevent the spread of airborne diseases.

**✓ Correct Answer:** B. Roofs 40%