English verb conjugation MUST HAPPEN

Regular verb: happen - happened - happened


Affirmation

Simple form

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it must happen
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V-ing form

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it must be happening
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Perfect

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it must have happened
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V-ing perfect

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it must have been happening
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Negation

Simple form

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it must not happen
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V-ing form

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it must not be happening
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Perfect

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it must not have happened
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V-ing perfect

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it must not have been happening
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Interrogative form

Simple form

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must it happen?
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V-ing form

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must it be happening?
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Perfect

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must it have happened?
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V-ing perfect

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must it have been happening?
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Interro-negative form

Simple form

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must it not happen?
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V-ing form

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must it not be happening?
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Perfect

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must it not have happened?
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V-ing perfect

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must it not have been happening?
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