UFO's & their Existence. Is it hoax? Unbelievable? Reality?

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Recently I have seen several video footages about UFO's & any one can see it? I got an idea from there that several wreckages of extra terrestrial objects have got into the hands of several powerful nations and they have already made replicas of the objects secretly to stunned the opponents. A recent sighting of UFO in china 2010 strengthens the idea. These nations are using this objects in the name of UFO for espionage purpose over the opponent nations. From the video footages I have seen that medics are also examining those alien bodies and got ideas but kept them secret from the world. Those who have ideas about USA's sector 51 could better understand everything. They have already developed flying objects similar to UFO's but not successful in travelling outer spaces. In my opinion UFO's does exist, life exists in other parts of the universe may be in other form but all the UFO sightings reported are not them. Instead some terrestrial objects with terrestrial living beings within them to hoax the world. What you think?