Part 2: Read the text below and choose the best answers

Solar collectors absorb heat from the sun’s rays. They can be used to effectively heat and cool buildings. The most common type of collector for space heating is a flat plate designed to absorb both radiation falling directly on it, as well as radiation scattered by the atmosphere. Collectors are usually panels of aluminum, copper, or steel. The collector is covered with glass or plastic. This layer allows short- wave radiation or light to enter the collectors. As the radiation passes through the glass or plastic, it is transformed from short-wave radiation to long-wave radiation – or heat. A transfer agent (air or water) is circulated through the collector and becomes heated. As it leaves the collector and travels through the heating ducts of a house, it warms the air inside the house or brings hot water to sinks, tubs, and appliances. With solar collectors. Storage is a problem: great amounts of heat must be stored for nighttime use and for use during cloudy days.

Solar collectors can heat and cold houses with heat absorbed from______.