按要求完成填空。

How is food put into cans? I am investigating it．(同义句)

I am investigating how ________　________ put into cans．

　　Long, long ago, people didn't have telephones 　　1　　 other modern ways to send messages to others, but they still could send messages 　　2　　 many different ways．A man put his ear to the ground．　　3　　 he heard the sound of the horses, he quickly ran to tell his people．He was a runner．That was one way to send messages．

　　People 　　4　　 sent messages by smoke．One man made a cloud of smoke．In the next place people saw the smoke and went on doing that, too．The message thus went from one place 　　5　　 another by smoke．

　　Much later, some soldiers kept many pigeons (鸽子)．These pigeons always flew back．When a soldier was sent far 　　6　　 from his place, he might carry 　　7　　 pigeon with him．He could write a message 　　8　　 put it on the bird' s leg．　　9　　 would fly back with the soldier's message．

　　These are some ways to send messages．　　10　　 you think of some faster ways?