Greenhouse gases let through a lot (but not totally all) visible light, while infrared light gets trapped in, or reflected from, the medium. That means that although visible light is able to pass through to us on the surface, the long wavelength infrared light, which is produced as a result of this visible light heating up everything on Earth, gets trapped on its way out of the earth's atmosphere, heating up the planet.
A good analogy is the effect that a sunny day has on the inside of your car when you enter it. The light comes in, the heat stays in. The glass windows of the car display similar, although more intense, properties to greenhouse gases. Hence the name "GreenHouse Effect"
Answer: C.) They reflect infrared light but let visible light pass through.
