Answer:
Option D. Car companies have developed hybrid cars.
Explanation: 
Nowadays car companies have developed hybrid cars. In hybrid cars, the cars are moved by using electric energy instead of fossil fuels. Hybrid cars uses batteries which can be charged by electricity and this store electricity is used to run cars. These types of cars reduce carbondioxide emissions and decrease occurs in air pollution. 
 
        
                    
             
        
        
        
Answer:
Organisms depends on physical and biological factors of an ecosystem.
Explanation:
Biological and physical changes cause shift in an ecosystem's populations because the population of organisms depends and greatly affected from the environmental factors such as temperature, moisture etc. These environmental factors causes change in the physical features of an ecosystem so when these changes occur in physical factors, it greatly affected the population of organisms.
 
        
             
        
        
        
Answer:
The answer is D. Double Helix
 
        
                    
             
        
        
        
Because nerves are the transmitters of messages from the brain to the structure, and all major nerves are found in the spinal cord leading out to the rest of the body. If the nervous tissue is damaged then the brain can no longer send messages to those parts of the body, and they an no longer react causint paralysis. 
Hope this helps. :)