How does this sentence introduce the passage's main ideas? This is a very real problem one that is finally being noticed by health experts and even by some school systems, which have already mover starting times to later in the morning ." (paragraph 2)

A It highlights the controversial steps school districts have taken and offers evidence to support the success of these steps.

B It describes the issues school districts face regarding scheduling and offers a potential solution to the problem.
C It highlights the validity of the problem involving teenagers sleeping habits and shows how the issue is being confronted .

D. describes how health experts are growing increasingly alarmed by the lack of concern regarding teenagers ' sleeping habits