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. 
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Question: Plants start growing on or near the rocks. The roots of the growing plants start to break up the rock. The plant acids dissolve the rock. The rock is broken down into smaller pieces. Erosion begins. 

Answer: How does weathering cause rocks to break apart?


Question: Water comes into contact with something made of iron. The water combines with carbon dioxide in the air to form carbonic acid. As the acid is formed, the iron starts to dissolve. Some of the water breaks down into hydrogen and oxygen. The free oxygen and dissolved iron bond together. They form iron oxide, which is rust. 

Answer: How does rust form?


Question: The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down. Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe. 

Answer:
Describe how an internal combustion engine works