短文改错：找出短文中有错误的地方划线并改正，每行只有一处错。
Hundred of years ago, news was carried ____
by people on foot or by a horse. ____
It takes people a long time to receive news. ____
Now it is possible to sending words and pictures____
in seconds. Billions of people learn about news
either by watching TV and by reading. ____
是虚数单位，
等于（ ）