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mustn’t have seen can’t have seen couldn’t see needn’t have seen
a, / a, the the, / the, the
mustn’t have seen can’t have seen couldn’t see needn’t have seen
They tell us which one of the tracks the universe will use. They enable us to alter the course of the universe. They give us information about the lunar surface. They determine which course the universe will take in the future.
can’t can you can’t we can we
ways of life marks of cars orbits of planets a course for racing.
in; at in the; at in; at the at; in the
Train engineers. General audiences. Professors of statistics. Young children.
to cry to laugh laughing cry
mustn’t have seen can’t have seen couldn’t see needn’t have seen