A、A swimming pool. B、A high ground. C、Under a tree. D、A closed car. D

In earliest times, men considered lightning to be one of the great mysteries of nature. Some ancient people believed that lightning and thunder were the weapons of the gods. In reality, lightning is a flow of electricity formed high above the earth.
   The American scientist and statesman, Benjamin Franklin, was the first to show the connection between electricity and lightning in 1752. In the same year he also built the first lightning rod. This device protects buildings from damage by lightning.
   Scientists estimate that there are about 2 billion flashes of lightning per year. Lightning hits the Empire State Building in New York City 30 to 48 times a year. In the United States alone it kills an average of one person every day.
   The safest place to be in case of an electrical storm is in a closed car. Outside, one should go to low ground and should not get under trees. Also, one should stay out of water and away from metal fences. Inside a house, people should avoid open doorways and windows and should net touch wires or metal things.