Review the expository writing prompt below.

Write an expository essay that informs your audience about a significant problem you aspire to solve when you grow up. Describe the problem in detail, its causes and effects, and explain two potential solutions for positive change. Support your ideas with well-researched evidence. Your expository essay must be based on this prompt and topic, and it must incorporate ideas and information found in at least three researched sources.
Use your best writing to complete an essay that

is focused on a central idea;
combines evidence from three credible sources with your own elaboration to develop your ideas;
is organized and includes transitions within and among ideas;
provides citations for quoted material and source ideas; and
demonstrates correct use of grammar and language appropriate to the task.

How many researched sources are required to be incorporated into this expository essay?
One researched source
Two researched sources
Three researched sources
Four researched sources

Three researched sources