Here's a problem to solve: Dawn brought a chocolate bar for lunch, but the chocolate melted in her backpack. Dawn wants to perform a scientific investigation to determine the reason her chocolate bar melted in her backpack. Which hypothesis should Dawn use for her investigation?

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

- A: Chocolate will taste better when melted.
 
- B: Chocolate will taste the same even when melted.
 
- C: If the chocolate is broken then the chocolate will melt.
 
- D: If heat is added to chocolate then the chocolate will melt.
 