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. 

Warm, moist air moves from south to north. Cool, dry air moves from north to south. The air masses meet. The conditions that form are not stable because the air masses are so different. Winds are directed in a certain way because of how the masses interact. An updraft results. Winds start to form circular patterns in the updraft. A tornado can result. 
How do tornadoes form?

The inner portion of the ring is formed during rapid spring growth. The tree's growth slows as the seasons change. The ring's outer growth is more dense. The growth of the tree pushes out the bark of the tree. The tree stops growing quickly in the winter. This seasonal "pause" in growth results in distinct rings in certain tree types. 
How do rings form inside the trunk of a tree?

A man and woman mate. Embryo is C. Embryo grows and develops into a fetus inside the woman's womb. The fetus is born. Begins to grow and develop through infancy and childhood. In the teenage years the human experiences puberty. Reaches sexual maturity. At 18 the human becomes an adult. Adult may procreate continuing the cycle. 

Describe the life cycle of a human