What does underscore mean in this context?
Two new studies underscore hopes, frustrations of revamped school lunches

http://www.washingtonpost.com/news/food/wp/2014/03/04/two-new-studies-underscore-hopes-frustrations-of-revamped-school-lunches/

Question

What does underscore mean in this context?
Two new studies underscore hopes, frustrations of revamped school lunches

http://www.washingtonpost.com/news/food/wp/2014/03/04/two-new-studies-underscore-hopes-frustrations-of-revamped-school-lunches/

Answer

It means emphasize. See definition 2: http://dictionary.reference.com/browse/underscore

Answer

They mean to further explain or talk about hopes, frustrations of  revamped school lunches.