It+be+强调成分+that/who-分句 原句：John gave Mary a present at christmas. It was John who gave Mary a present at christmas. It was Mary that John gave a present to at . It was a present that John gave Mary at . It was at Christmas that John gave Mary a present.原句: John gave Mary a present at christmas. It was John who gave Mary a present at christmas. It was Mary that John gave a present to at 1 It was a present that John gave Mary at 1 It was at Christmas that John gave Mary a present. It + be + 强调成分+ that/who-分句