before, discover , fast, in, come, watch , so, fast it, ago , shine, not can
Light travels at a speed (速度) which is about a million times 1 ____________than that of sound. 2___________one second, light travels about 300,000 kilometers, but sound travels only 340 meters. You can get some idea of this difference by 3 ______________the start of a running match. If you stand far away from the starter(发令员), you can see smoke 4 ____________from his gun 5____________ the sound reaches your ears.
The fast speed of light produces some strange facts. The nearest star is 6 ____________far away that light which you can see from it tonight started to travel to you four years 7____________at a speed of nearly two million kilometers every minute. The light from some of tonight’s started on 8 ____________journey towards you even before you were born.
So, if we want to be honest, we 9 ____________say, “The stars are shining brightly tonight.” We have to say, “The stars look nice. They were 10___________four years ago but their light has just reached our earth. ”
Key
（三）1.faster 2.In 3. watching 4. come 5. before 6. so 7. ago 8. its 9. cannot 10. shining