In this task, you are given a paragraph, and your task is to construct a question from the given passage. Construct question in such a way that (i) it is well explained in the paragraph, (ii) the words may/may not be present in the paragraph, (iii) it should start with what/how/describe. Avoid creating a question that (i) is just relevant to one or two sentences, and (ii) not relevant to passage. 

[EX Q]: Dissolution of limestone forms caves. Rain gets carbon dioxide from the air. When rain goes into soil it creates an acid. The acid dissolves the limestone along cracks. Some will dissolve enough to form caves. 
[EX A]: How do caves form?

[EX Q]: The flu virus has receptors, which are like viral Velcro, on the surface of the virus particle. The receptors will lock onto a target cell using these chemical receptors on the surface, which docks onto the cell surface. The receptors  then go into the cell. The receptors use it like a factory. The receptors take it over and make it produce thousands or in some cases millions of copies of new viruses. The copies come streaming out of the cell. The copies infect other cells to make more viruses, or they escape from the body and infect a new victim. 
[EX A]: How does a virus cause disease?

[EX Q]: You breathe in. Diaphragm and other muscles expand to allow room for your lungs to fill. The air flows into the narrow bronchioles in the lungs. From the bronchioles to the alveoli. The oxygen enters into the bloodstream. Is switched with the carbon dioxide in the bloodstream. The carbon dioxide enters through the alveoli. Through the narrow bronchioles. Into the lungs. The carbon dioxide is exhaled out of the body. 
[EX A]:
How do lungs work?