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:
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:
Water is exposed to heat energy, like sunlight. The water temperature is raised above 212 degrees fahrenheit. The heat breaks down the molecules in the water. These molecules escape from the water. The water becomes vapor. The vapor evaporates into the atmosphere. 
answer:
Describe the process of evaporation


question:
Oxygen-depleted blood enters the heart on the right atrium. The atrium contracts. Blood flows from your right atrium into your right ventricle through the open tricuspid valve. When the ventricle is full, the tricuspid valve shuts. The ventricle contracts. Blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs. The lungs oxygenate the blood. The oxygenated blood goes into the left atrium. The left atrium sends the blood throughout the body. 
answer:

How does the heart work?


