Good sleep hygiene, the behaviors that promote good sleep, will help ensure that middle schoolers get enough sleep.

How does the author develop the key concept in this sentence?
by giving an example
by giving an example

by defining an important term
by defining an important term

by describing specific steps to solve a problem
by describing specific steps to solve a problem

by comparing important ideas

The author develops the key concept in this sentence by defining an important term - "good sleep hygiene."