⑥One day Newton sat at his desk.⑦ He was studying very hard. His servant came into the room. ⑧ He left an egg on his desk.⑨ There was a watch on the desk.⑩ Into the boiling water in the kettle Newton put the watch instead of the egg.
英语基本句型（Basic Sentence Patterns）(2)
it and thought： ③ “Why did an apple fall?”④He studied very hard.⑤ Later he found out the reason.