câu1 comlete the sentences with the words or phrases in the box galaxy/planet/flying saucer/ solar system/astrounaut/outer space/space buggy/weighless/aliens/traces 1A..........flying saucer is sometimes referred to as an Unidentified Flying Object (UFO) 2An .............astronaut is a person who is traineeeed for travelling in a spacecraft 3Researches made the amazing findings of ............traces ........... of water on Mars 4A.............space buggy is a vehicle used for driving on the moon 5Our..............solar system ...........is made up of the sun and all the objects that travel around it 6 Earth is the only known to be habitable to........... planet ...............life 7 Do you believe ............aliens ....................exist on other planets? 8 Spacecraft are vehicles used for travel in.........outer space 9Our ........ galaxy,the Milkyl,Way, consists or 100-400 billion stars 10.Astronauts on the orbiting space station are ...............weighless because they do not experience a force of gravity