Answer:
The freshwater trout requires a lower salt ions to function.
Explanation:
 
        
             
        
        
        
With the advent of industrialization, several trees have been cut at an alarming rate for raw materials and various other purposes. This felling of trees can be regulated by selective cutting, clear-cutting and shelterwood cutting.
Forest fires are one of the common causes of loss of forests. Sometimes the forest land is set on fire to make the land available for commercial purposes. Once cleared, there can be no vegetation. Natural forest fires are also responsible for the destruction of huge forest covers. Latest fire fighting techniques should be adopted to conserve the forest. However, forest fires are an important part of the ecosystem and it helps replenish nutrients in the soil from dead and decaying matter.
More trees should be planted to increase the forest cover. Trees should be selected according to the geographical conditions of a particular region and proper care should be taken during the growth of trees.
Prevention of exploitation of forestry and forest products is necessary for the conservation of forest.
The existing forests should be protected from diseases by spraying chemicals, antibiotics or development of pest-resistant strains of trees.
 
        
             
        
        
        
Simple answer:
When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white. Warmer water temperatures can result in coral bleaching. ... This is called coral bleaching. When a coral bleaches, it is not dead.
More in depth explanation:
Exposure to higher (100 and 1000 µg l-1) diuron concentrations for 96 h caused a reduction in ΔF/Fm¹, the ratio variable to maximal fluorescence (Fv/Fm), a significant loss of symbiotic dinoflagellates and pronounced tissue retraction, causing the corals to pale or bleach.
Hope this helped :)
 
        
             
        
        
        
Its either a or d 
a because if someone takes a photo of the wings they could see how the wings work
or
d because then the person could see the colors in the pictures