A toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies.
        
             
        
        
        
B is the right answer:
A more biodiverse ecosystem has a higher chance of adapting to species changes. 
 
        
             
        
        
        
Water molecules bond to each other in a covalent bond where they stay connected. They also have poles like a magnet, making it a polar molecule.
If water is no longer polar the surface tension would lower to the point where ice can no longer float, the water would freeze, cooling the climate considerably.
        
             
        
        
        
Answer:
The fourth plant that receives pure water is the control group. 
Explanation:
The election of a control group is essential in an experiment. Its principal purpose is to allow the discrimination of the results obtained by the treatment in the study, in this case, <em>the different concentrations of salty water that each plant receives</em>. The control group provides a reference point. It must be selected from the same population of the treatment groups. Both groups must be similar in every variable that might influence the results, <u>except for the study treatment.</u>
 
        
             
        
        
        
<span>Because the bases can be arranged in many different combinations</span>