Some plants are grown in cold frames. Cold frames are

• A. Frames covered but not heated artificially
• B. Heated buildings with transparent roof and sides
• C. Frames covered and heated artificially
• D. Cold pits used only for bulb storage

Answer: (A)

Cold frames are simple, unheated shelters that use the sun’s heat to warm the air around plants. They’re frames covered with a transparent material (like glass or clear plastic) that trap heat, creating a warmer microclimate to protect seedlings and extend the growing season without relying on artificial heating. Because there’s no heating system, the inside temperature depends on sun exposure and outside conditions, and you can vent or close the frame to manage temperature. This setup is different from heated buildings or greenhouses, which have artificial heat, and from cold pits used for storage.