instruction:
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. 
question:
Air enters the nose or mouth and travels through the windpipe into the lungs. The lungs have a series of smaller and finer tubes and sacs. Air reaches the smallest and finest air sacs called alveoli. Oxygen travels from the alveoli into the blood. Oxygen-rich blood is carried to the heart. Oxygen-rich blood is pumped throughout the body by the heart. Cells take in the oxygen rich blood and release carbon dioxide rich blood. The carbon dioxide rich blood travels to the lungs. Carbon dioxide travels through the throat and is exhaled. 
answer:
How do the lungs work?


question:
Water in the clouds becomes very cold. The cold water forms ice crystals. The ice crystals grow by absorbing surrounding water droplets. Form snowflakes. The snowflakes fall to the ground. 
answer:
How does snow form?


question:
A plant dies. The remains of the plant are buried very fast in sediment. The soft parts of the plant decay. The hard parts of the plant are replaced with minerals. The sediment turns into rock. The rock erodes. The fossil appears on the surface of the ground. 
answer:

Describe the process of fossilization


