Answer:They came to realize that a bull was chasing them when they saw Tom running towards them and asking them to run too.
Explanation: "A sudden stamping upon the frozen ground arose from beyond the bushes."
" Tom leaped through the bushes and looked down the hill. There sounded the thundering of hoofs and the boy sprang back to the side of his sister and her chum with a cry,'Run!' he gasped."
