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EXERCICE / savoir employer le preterit simple ou le present perfect Conjuguez les verbes entre parenthèses au PRETERIT SIMPLE ou PRESENT PERFECT. 1) Yesterday thousands of UFOs ... (appear) in the sky. 2). .... spaceships already. (land) on the island of Vanutu? 3) The very same night, one witness round faces and three eyes. (see) twenty small aliens with large all 4) The spaceships are empty. The aliens (disappear). It's very strange. already 5) Professor Paul Johnston said: " I'm sure aliens (visit) our planet". 6) When .it (happen)? 7) There (be) many reports of UFO sightings so far. 8) Astrobiology forms in the universe so far. (not show) evidence of the existence of other life​