Tom goes to see his grandfather with his father in the train

Tom goes to see his grandfather with his father in the train.Tom often puts his head out of the window.His father says.“Tom,don't your head out of the window.” But Tom goes on putting his head of the window.
　　His father takes Tom's hat quitely and hides it behind his back and says to Tom.“You see your hat is gone.” Tom is afraid.His father says.“Well,whistle(吹口哨) once.Perhaps your hat will come back.” Tom whistles.His father puts his hat on Tom's head quickly,“Oh!It's wonderful,” Tom laughs and says.He quickly takes his father's hat and throws it out of the window “Now it's your turn to whistle,Dad!” He says happily.
1．________ and his hat is on his head.
A、Tom whistles　　B、Tom's father whistles 　C、Both Tom and his father whistle