Review the passage:
Chewing the dry, tough, whole-grain bread bought from the health food store.
Lorena tried to enjoy her lunch. Fantasizing about a
juicy cheeseburger on a soft white bun did not improve the taste of the
soy product sandwiched between leaves of organic lettuce.
You chose the third part, Fantasizing about a juicy cheeseburger on a soft white bun did not improve the taste of the soy product sandwiched between leaves of organic lettuce. This part has a main clause: Fantasizing is the subject; did improve is the verb. A fragment will not have a main clause.