Here is the passage again:
Peering around the other students in line, Sylvia tried to see the lunch
choices. The cafeteria selections were disappointing.
For example, greasy fried chicken, soupy sweet-n-sour
pork, and a gray mystery meat floating in translucent, lumpy gravy.
The third part is an afterthought fragment. It has neither a subject nor a verb, so there is no main clause, the essential element in all sentences.