<span>Danforth wants him to sign his name on a written statement</span>
The function of the noun phrase <em>Green, leafy vegetables </em>in this sentence is that of the subject of the sentence.
What contains important vitamins for a healthy body? - Green, leafy vegetables.
An example of a challenge facing the American people during the late 20th and early 21st century is public education. The American democracy depends on an educated and well informed citizenry.