Answer:
First off you can cross out the last one because $3 is for 6 waterbottles, which leaves options 1,2, and 3. Since the rate shows that every 5 water bottles is $2 that mean continueing from 10 water bottles with $4 we have 15 with $6, 20 with $8, and 25 with $10. So that means the correct answer is the first option.
