He was a single father, raising a 5-year-old boy alone. He worried about his son growing up without a mother to care for him. One day he went away on business, leaving the child alone. He was worried about the child all the way, not knowing if he had eaten. But his child always told him not to worry. He went home quickly after finishing his work. When he got home, the child was deep asleep. He was tired out. When he was about to sleep himself, he was surprised to find an overturned bowl of noodles under the quilt. He spanked his sleeping son angrily:"Why are you so naughty, making the quilt dirty? Who will wash it?" It was the first time that he had hit his boy after his wife's death. "I haven't," the boy explained with tears in his eyes. "This is your supper, Daddy." In order to let his father eat dinner as soon as he got home, the boy cooked two bowls of noodles: one for himself, the other one for his father. He was afraid his father's noodles would get cold, so he placed them under the quilt to keep them hot. Hearing this, the father hugged his boy tightly without saying a word. According to the passage we know the boy only had   _  .
a grandfather a mother a father a grandmother