A freezer room evaporator coil has developed a heavy frost buildup. Which of the following best describes the effect on system performance and the correct corrective action?

1. A. Frost improves heat transfer by increasing the coil surface area; no corrective action is required until the frost bridges the fin spacing
2. B. Frost lowers the evaporating temperature, causing suction pressure to rise; the metering device should be adjusted to reduce refrigerant flow
3. ✓ Frost insulates the coil and blocks airflow, steadily reducing capacity; the coil must be defrosted periodically by stopping the system, electric or hot-gas heating, or waterCorrect
4. D. Frost increases the thermal mass of the coil, slowing temperature swings in the space; defrost only when the compressor begins short-cycling