Solar ponds are bodies of water in which circulation is incomplete and there is a very high salt concentration that increases with depth. This vertical change in salinity serves to trap heat because concentrated brine in the lowest water level acts as a collector and storage area for solar heat, while the less saline, lighter water at the upper levels provides insulation. Heat is thus retained in the depths.
An artificial pond of this type has been constructed on the western shore of the Dead Sea in Israel in order to test its suitability as a source of low-grade heat for conversion into electricity. An immediate threat to the success of the venture was the growth of algae. Water in solar ponds must be kept maximally transparent to allow penetration of light to the deep storage area. Therefore, any particles of matter in the water, such as algae cells, that scatter or absorb light will interfere with the collection of heat.
One proposed method of controlling the algae was the application of an algicide. However, the Dead Sea is a closed body of water without any outlet and as such is very easily contaminated. Extensive use of chemicals in numerous future full-scale solar ponds would lead to such contamination of the Dead Sea, which now enjoys a lucrative tourist trade.
A recent experiment has supplied a more promising method for controlling the algae. To repress the algae cells' capacity for accommodating themselves to environmental changes, the water in the solar pond was first made more saline through evaporation and then diluted by a rapid inflow of fresh water. This shock reduced the cells' ability to regulate the movement of water through their membranes. They rapidly absorbed water, resulting in distortions of shape, increase in volume, and impairment to motility. Their buoyancy adversely affected, the cells sank to the bottom of the pond, where they encountered the hot waters of the storage layer and were destroyed. This method allows for effective control of nuisance algae while leaving solar ponds as one of the cleanest technologies providing energy for human use.
It can be inferred from the passage that which of the following is true about the salinity and temperatures of the highest and lowest water layers in a typical solar pond?
The bottom layer is both highly saline and quite hot, while the top layer is less saline and cooler.
The two layers have similar salinity levels, but the bottom layer is hotter than the top.
There is no way to predict the salinity and temperature of the different water layers in different solar ponds.
The bottom layer is less saline and quite hot, while the top layer is more saline and cooler.
The top layer has both higher salinity and higher temperatures than the bottom layer.
这道题是让我们推断两个水层的盐度和热度。盐度问题定位在“This vertical change in salinity serves to trap heat because concentrated brine in the lowest water level acts as a collector and storage area for solar heat, while the less saline, lighter water at the upper levels provides insulation.” 这句话直接说明了盐度是下层的比较高。热度问题定位在最后一段的“Their buoyancy adversely affected, the cells sank to the bottom of the pond, where they encountered the hot waters of the storage layer and were destroyed.”。这句话说细胞掉到下面有部分会因水热被破坏，也就是说下层的水比上层的热。下面的“选项分析”只翻译选项。