It isn't informing the readers how swimming lessons can be expensive, it never said that in this sentence.
it doesn't really entertain readers with a fun suggestion about swimming, entertainment is more like a book about an adventure other than someone giving information about swimming.
The author never said he had a swimming class and specifically said "...some lessons at your local pool". you can be located anywhere and it doesn't say to join his swimming lessons, it doesn't even say he has his own class to take swimming lessons.
C just makes the most sense because yes it is persuading, the author gave reasons why you could take lessons and the other answers are less true than this.
