The inference about the boys that is best supported by the text is c) The candy means more to the boys than the bread, because getting it would be a rare time they had something that met more than their basic needs.
In the text, during the scene in the store, we see that the boys come with their father to buy a loaf of bread because that's what the family can afford if they want to make it to California. When they are leaving, the only textual reference we get is that the father "sees the boys eyeing the peppermint candy" and he asks how much it costs.
We cannot interpret that they wanted to steal it or if they prefer the hamburgers instead of the bread. What we can infer is that the boys know that their family have budgeted carefully and cannot spend much money on food, even less on candy. Therefore, candy means much more for them than bread. The fact that their father buys the candy for them can be interpreted as "satisfying" that extra "need" in the context of the Great Depression when boys were deprived of a more relaxed infancy.