English verb conjugation SHOULD HAPPEN
Regular verb: happen - happened - happened
Affirmation
Simple form
--
it'd happen
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V-ing form
--
it'd be happening
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Perfect
--
it should've happened
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V-ing perfect
--
it should've been happening
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Negation
Simple form
--
it shouldn't happen
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V-ing form
--
it shouldn't be happening
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Perfect
--
it shouldn't have happened
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V-ing perfect
--
it shouldn't 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
--
shouldn't it happen?
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V-ing form
--
shouldn't it be happening?
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Perfect
--
shouldn't it have happened?
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V-ing perfect
--
shouldn't it have been happening?
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