A is incorrect because that states that their are 9 guides.
B is incorrect because then 3 people wouldn't have rafts.
C is correct because it will have 9 people and 1 guide which is 10 people.
D is incorrect cause then the other 2 guides would have no job.
E is incorrect because 3 customers would have no guides.
F is correct because their are 9 costumers per raft per guide.