Completethepassagewithfollowingwordsorphrases.（Fill in one of the letters）A.performB.heardC.tiedD.senseE.acrossF. resultsG. rulerH. placedI. deliverJ. trainedNext time you see a pigeon flying1 the sky, look at it carefully! Is it holding a can? Or a camera? Or wearing a backpack? If it’s a carrier pigeon, it just might be a working bird.You’ve probably2 of working dogs that help police officers, or horses that help farmers. Did you know that carrier pigeons can be3 to help people too? What kind of jobs do these birds4?Carrier pigeons can be trained to carry messages to people. The note is5into a small skinny can. The can is6to the pigeon’s leg. Then the pigeon flies off to7the note. Carrier pigeons are good messengers because they’re fast and can fly long distances. They also have a good8of direction. They can even reach places that people can’t. More than 800 years ago, Genghis Khan, an Asian9set up pigeon post offices across his lands! As recently as 2010, Cuba used pigeons to send election10to its mountain people.