For hot desert locations with access to seawater, a new greenhouse design generates
freshwater and cool air. Oriented to the prevailing wind, the front wall of perforated
cardboard, moistened and cooled by a trickle of seawater pumped in, cools and moistens
hot air blowing in. This cool, humidified air accelerates plant growth; little water
evaporates from leaves. Though greenhouses normally capture the heat of sunlight,
a double-layered roof, the inner layer coated to reflect infrared light outward, allows
visible sunlight in but traps solar heat between the two layers. This heated air, drawn
down from the roof, then mixes with the greenhouse air as it reaches a second
seawater-moistened cardboard wall at the back of the greenhouse. There the air
absorbs more moisture, which then condenses on a metal wall cooled by seawater, and
thus distilled water for irrigating the plants collects.
4. It can be inferred that the greenhouse roof is designed to allow for which of the
following?
A The avoidance of intense solar heat inside the greenhouse
B The entry of sunlight into the greenhouse to make the plants grow
C The mixture of heated air with greenhouse air to enhance the collection of
moisture
解析说,Choice B is correct: the coating on the inner layer of the roof allows visible sunlight
into the greenhouse.