Your answer will be C.
This is because a sentence in a paragraph or story is usually about the topic or related to the topic no matter what it is.
Hope this is helpful to you!!^_^
1. down the sidewalk | to the hospital
2. at 11 P.M. | until 7 P.M.
3. in a hospital
4. After doctors and nurses | for administrators, dietitians, and lab workers
5. of caring professionals (Object of preposition would also be dietitians and lab workers.)
6. in the gift shop | as a volunteer
7. for the children | with serious illnesses
8. with flashing lights | onto the scene
I believe it's 3, parenthetical expression
