0.78÷0.2=____÷2;
64÷0.08=____÷____.
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.
下列属于不尊重他人隐私或侵犯他人隐私权的行为有( )
①网站将其注册会员的照片、电话号码、家庭住址等信息整理成册,卖给信息公司
②进别人房间要先敲门
③警方为尽快抓捕犯罪嫌疑人,将某通辑犯的照片、姓名及相关信息,通过媒体进行公开
④小林的妈妈偷看他的日记
从1~10这10个不相等的自然数中每次取出2个数求和,要使它们的和小于10,不同的取法有____ 种.
下列各数中,立方根一定是负数的是( )