gmatprep死海一题请教（搞懂了）

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冒险,风险was the growth of algae. Water in solar ponds must be kept maximally transparent to allow penetration渗透,侵透,侵入of light to the deep storage area. Thearefore, 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 有利益的,获利的,合算的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.
   运动性,自动力 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讨厌的东西algae while leaving solar ponds as one of the cleanest technologies providing energy for human use.

Q1. 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?

A.     The bottom layer is both highly saline and quite hot, while the top layer is less saline and cooler.

B.     The two layers have similar salinity levels, but the bottom layer is hotter than the top.

C.     There is no way to predict the salinity and temperature of the different water layers in different solar ponds.

D.     The bottom layer is less saline and quite hot, while the top layer is more saline and cooler.

E.      The top layer has both higher salinity and higher temperature than the bottom layer.

答案不是D而是A呢 .This vertical 垂直的change in salinity serves to trap heat because concentrated brine盐水in the lowest water level acts as a collector and storage area for solar heat, while the less saline含盐的,
   lighter water at the upper levels provides insulation, Heat is thus retained in the depths. 从这句话能得出A