First World War, also known as the World War I (WWI), was a global war centered in Europe that drew in all the world's economic great powers of that time.
You got a .rar file and you don't how to open it, some one asked you to send him "a rar file" or you just need a good archiving software? Download and install WinRAR.
I know a lot of people who do not care for wearing a helmet when on a bike for a common reason of looking silly or it will mess up their hair. This amazing invisible helmet could be quite revolutionary.