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. 

Input: Consider Input: Water comes through a filter. The filter has small pores to catch pollutants. The filter will catch chlorine, heavy metals, and other chemicals. The filter allows water and mineral ions like fluoride to pass through. The water on the other side of the filter is much cleaner. 

Output: How does a water purifier work?


Input: Consider Input: Coal is loaded into the firebox. The boiler produces steam under high pressure. The steam generated in the boiler flows down into a cylinder. Just ahead of the wheels, pushing a tight-fitting plunger, the piston. The piston is connected to one or more of the locomotive's wheels through a kind of arm-elbow-shoulder joint called a crank and connecting rod. As the piston pushes, the crank and connecting rod turn the locomotive's wheels and power the train along. An outlet valve opens and the piston pushes the steam back through the cylinder and out up the locomotive's chimney. 

Output: How does a steam engine work?


Input: Consider Input: The virus finds an animal cell. The virus attaches to the cell's surface. The cell swallows the virus. The virus' RNA is released into the cell. The cell mistakenly reads the virus' RNA instead of its own. The cell creates new viruses. The animal cell releases the new viruses. The new viruses can infect more cells. 


Output: How does a virus infect an animal?