PLEASE HELP!!

Theme Park Rules
1. No outside food allowed inside the park; water is allowed.
2. Free re-entry into the park with a hand stamp.
3. Re-entry into the parking lot costs $2.
4. Food and drink are allowed in the outside picnic area.

Friend Alisa, Bailey, Chelley, and Diana visited a theme park. Two hours after entering the park, they decided they needed some water to drink.

Which girl made the most financially responsible decision?

(Assume there is no tax on any of the purchases.)
A.
Diana left the park in her car, bought two $3 water bottles at the corner store, then re-entered the parking lot.

B.
Alisa bought two $5 water bottles inside the park.

C.
Bailey bought one $5 water bottle inside the park and refilled it once at a water fountain.

D.
Chelley bought two $1 water bottles and left them in her car in the parking lot.