The correct answer to this open question is the following.
You forgot to include the statements/options for this question. However, we can say the following.
The statement is best supported by the dialogue is "Grandpa believes that it is time to begin preparing for his death."
This is correct because, before this idea of the excerpt, Grandpa also said: "You found the money in my boots?" he asked Mom. "Martin did," she answered, and roused herself to scold. "Grandpa, you shouldn't have carried so much money. What if someone had stolen it from you?"
So Grandpa is angry because its family is trying to steal money to buy their own things. However, he loudly laughs knowing that he has his own money hidden inside his boots, and it won't be an easy task for his family to take the money out from his boots.