In old times，man considered lightning to be one of the great mysteries（神秘事物）of nature．In fact a single flash of lightning 1.6 kilometers long has enough electricity to light one million lamps．
The American scientist，Benjamin Franklin，was the first to suggest that lightning is in fact electricity formed between the earth and clouds high above．It happened in 1752．In the same year，he also built the first lightning rod（避雷针）to protect buildings from being struck by lightnings．
Modern science has discovered that lightning is very strong and powerful．A lightning between a cloud and the earth may be as long as 13 kilometers，and travels at a speed of 30 million meters per second．Scientists have the opinion that there are about 2000 million flashes of lightning per year．In the United States alone，it kills almost one person per day．
The safest place to be in during an electrical（电的）storm is a closed car．Outside，one should go close to low ground for cover and not stop under a tree．Also one should stay out of water and away from metal fences．Inside a house people should keep away from open doorways and windows and not touch wires or metal things．
【小题1】From this passage we know lightning is____．

Linda loves her dog Davy.  They went to New York last Saturday.  While Linda was 1    a newspaper at the railway station the dog got out of his box and ran away. The station was 2    and Linda couldn’t see Davy anywhere. When Linda 3    his name, some people looked at her but Davy didn’t 4   . Then she called the police. While she was talking on the 5   , Davy met another dog outside the station.  While the police were coming,  Linda  walked  around the station and called Davy’s name.   She  didn’t 6    about looking outside the station. Finally, a little boy said to her, “Did you look outside? I 7   a big black dog when I came in.” When Linda 8   saw Davy, he was jumping and running with another dog. There was a police officer 9    them. The police officer said to Linda, “ I think my dog 10    your dog.”