Is this a riddle? I think it is a lettuce vegetable!
An abstract word are things like feelings, ideas, concepts and qualities
The correct answer is the main idea
The main character is the girl ( the salesman could be considered one too but since you said character not characters its most probs the girl). The story takes place mostly at the store since thats her destination, the place where she forgot the money, and the place that had sympathy on her when she did (basically where all the events took place). Finally, the information that makes the readers want to continue reading is perhaps the fact that she will pay the store back which sort of already develops a plot for the next bit.
