父親也是， then held the nail in his mouth and bit it with his teeth. then he used the hammer as a ruler to make a mark on the tree trunk along the direction of his son s head，再用錘子當標尺沿著兒子頭頂的方向在樹干上做了個標記，父與子——一年之后，釘子怎么高了？ but that the small tree grows faster tha