b. he is does not want anyone to come looking for him
Huck is tired of the adults in his life deciding things for him. His father is abuse and living in town is too constricting for the free-spirited boy. He wants people to leave him alone to have his own adventures and live his own life. There are other advantages that he thinks of to having people think he's dead, but the real reason is that he just wants to be left alone and not have anyone come looking for him.