Final answer:
Greenhouses use fiberglass as it helps trap solar radiation and heat energy, creating a warmer environment for plants.
Step-by-step explanation:
Greenhouses use glass, specifically fiberglass, because it traps solar radiation released from the sun. The glass allows visible light from the sun to pass through, which is absorbed by plants, soil, and surfaces and heats them. However, the glass blocks the infrared radiation produced by the heated objects, thereby trapping the heat energy inside the greenhouse and raising the temperature within.