中帆

例句：

1. 1. The ship's mast is made of wood and has a wooden keel.
   这艘船的桅杆是用木头做的，船底也是木制的。
2. 2. The sails on the boat are made of silk and have a silk keel.
   船上的帆是用丝绸做的，船底也是丝绸做的。
3. 3. The sailors were busy fixing the mast and keel.
   水手们忙着修理桅杆和船底。