?1.The spaceship couldn't have reached the correct altitude by the time the rockets separate from it.
2.The spaceship could have reached the correct altitude by the time the rockets separate from it.
3.The spaceship can't have reached the correct altitude by the time the rockets separate from it.
4.The spaceship can have reached the correct altitude by the time the rockets separate from it.
Are all four sentences correct?
Can 'could have done', 'couldn't have done, 'can have done' or 'can't have done' be used with reference to the future?
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