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(诚实), 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. "

参考答案：

1.faster

2.In

3.watching

4.come

5.before

6.so

7.ago

8.its

9.cannot

10.shining