English verb conjugation SHOULD HAPPEN
Regular verb: happen - happened - happened
Affirmation
Simple form
--
it should happen
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V-ing form
--
it should be happening
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Perfect
--
it should have happened
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V-ing perfect
--
it should have been happening
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Negation
Simple form
--
it should not happen
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V-ing form
--
it should not be happening
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Perfect
--
it should not have happened
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V-ing perfect
--
it should not have been happening
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Interrogative form
Simple form
--
should it happen?
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V-ing form
--
should it be happening?
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Perfect
--
should it have happened?
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V-ing perfect
--
should it have been happening?
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Interro-negative form
Simple form
--
should it not happen?
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V-ing form
--
should it not be happening?
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Perfect
--
should it not have happened?
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V-ing perfect
--
should it not have been happening?
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