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. 
Q: The growing season starts. Bark grows on a tree. The inside of the tree grows. The bark is pushed out around the tree trunk. The bark leaves a ring. The growing season slows down and ends. 
A: 
How do rings form inside the trunk of a tree?