The correct answer is option A- HIV virus.
HIV virus is an example of enveloped virus, that has the ability to infect a host cell by attaching itself to it and fusing with the host cell. Once infected, the virus leaves the host cell and moves to another cells to infect them. The HIV virus contains glycoprotein spikes to attach to the host cell. 
 
        
                    
             
        
        
        
Compressibility is a chemical property because it’s made more compact
        
             
        
        
        
I believe it's A, but I could be wrong. I apologize if I am so. I will do further research and get back to you
        
                    
             
        
        
        
Production of energy using water power
Using electricity or energy-saving products, creation of technology to capture sulfur dioxide are the processes that can be taken into account. 
<h3><u>Explanation</u>:</h3>
Acid rain is a very serious issue in the urban areas now a days. Acid rain forms due to the excessive production of gases like sulphur dioxide, nitrogen oxides etc which are beyond the level of absorption by the environment. This gases go up in the atmosphere and they mixes with cloud water to form corresponding sulphuric acid and nitric acid. These acids come along the rain and decrease the pH of the water bodies as well as soil.
If we start using water as the source of our energy production, then we can eliminate the use of coal and other fossil fuels which are chief sources of these gases. 
If we can grow some technology to capture these gases before they are released into the environment, then also there will be less problems. Technologies like alkali bath are not so operative in large scales. 
We can use electricity in boilers and other places where still, fossil fuels are brunt to produce the heat so that sulphur oxides don't come out.