should happen
Verbo regolare: happen - happened- happened

Affermazione 	
Forma semplice 	Forma con V-ing 	Perfetto 	Perfetto con V-ing 	
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it should happen
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it should be happening
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it should have happened
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it should have been happening
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Negazione 	
Forma semplice 	Forma con V-ing 	Perfetto 	Perfetto con V-ing 	
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it should not happen
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it should not be happening
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it should not have happened
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it should not have been happening
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Forma interrogativa 	
Forma semplice 	Forma con V-ing 	Perfetto 	Perfetto con V-ing 	
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should it happen?
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should it be happening?
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should it have happened?
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should it have been happening?
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Forma interro-negativa 	
Forma semplice 	Forma con V-ing 	Perfetto 	Perfetto con V-ing 	
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should it not happen?
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should it not be happening?
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should it not have happened?
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should it not have been happening?
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