Robert and Henry were going home from school, when, on turning a corner, Robert1out, "A fight! Let us go and see!" "No," said Henry; "Let us go quietly home and avoid this quarrel. We have2to do with it, and may get into trouble."

    "You are not a brave boy, and afraid to go, "said Robert, and off he ran. Henry went straight home, and in the afternoon went to school, as usual,3 Robert had told all the boys that Henry was a coward, and they laughed at him a great deal.

    A few days4, Robert was bathing with some schoolmates and 5his depth. He struggled and screamed for help, but all in vain. The boys 6 had called Henry a coward, got away from the water as fast as they could, but they did not even try to help him. Robert was fast 7, when Henry threw off his clothes, and sprang into the water. By great effort, and8much danger to himself, he brought Robert to the shore, and thus saved his life.

    Robert and his schoolmates were9at having called Henry a coward. They admitted that he had more10than any of them.

    Never be afraid to do good, but always fear to do evil.

一汽车以108 km/h的速度沿一长直的高速公路行驶，试求站在路旁的人观察到该汽车长度缩短了多少？已知此汽车停在路旁时，测得其长度为3 m.

铁的化合价是 ____

  170002088米读作（   ）

遗传病是由于人体内   ____    、 ____ 或____ 发生变化而引起的。