Here's a problem to solve: During an experiment, a class heated a balloon that had an initial circumference of 25 cm. The circumference increased to 27 cm. Which is the best conclusion that can be drawn?

Among the 4 following options, which is the correct answer?

- A: The molecules inside the balloon lost energy to the outside.
 
- B: The molecules inside the balloon gained energy from the heat.
 
- C: The energy of the molecules inside the balloon remained the same.
 
- D: The molecules inside the balloon were escaping outside.
 