Answer:
The sentence that best explains the motivation behind the stranger's interest in Elisa's chrysanthemums is He wants to encourage Elisa to think kindly of him so she will give him some money.
Step-by-step explanation:
The stranger in the story is a mender of pots and a sharpener of scissors and knives, he is looking for possible clients, and he pretends to be interested in the topics that Elisa is interested in to get her sympathy and latter convince her to hire him for his services, it is shown at the end of the story when he leaves the chrysanthemums on the road that he only had a commercial objective.