In recent years, with more and more cars on the road, flying robots are used to deliver(递送) mails. Flying robots can 1mails to people's houses without having to deal with heavy2.But they will spend too much time in returning. A research center is trying to improve its flying robots with the3of homing pigeons(信鸽).
Homing pigeons are pigeons that are4trained to fly home from somewhere else. In tests, researchers5that homing pigeons were6efficient(高效的) than flying robots at returning to their home. So the research center is trying to use a flying robot, together with a7, to deliver mails. After the robot finishes its tasks, it can8the pigeon back in the shortest possible time.
Although it will cost more money to9pigeons, the research center says that it can10time. And the time it saves will make up for the cost.
