English verb conjugation CAN HAPPEN

Regular verb: happen - happened - happened


Affirmation

Simple form

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it can happen
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V-ing form

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it can be happening
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Perfect

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it can have happened
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V-ing perfect

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it can have been happening
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Negation

Simple form

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it cannot happen
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V-ing form

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it cannot be happening
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Perfect

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it cannot have happened
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V-ing perfect

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it cannot have been happening
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Interrogative form

Simple form

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can it happen?
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V-ing form

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can it be happening?
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Perfect

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can it have happened?
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V-ing perfect

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can it have been happening?
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Interro-negative form

Simple form

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can it not happen?
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V-ing form

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can it not be happening?
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Perfect

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can it not have happened?
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V-ing perfect

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can it not have been happening?
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