could happen
Regelmä&szlig;iges Verb: happen - happened- happened

Bestätigung 	
Einfache Form 	Form mit V-ing 	Perfekt 	Perfekt mit V-ing 	
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it could happen
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- 	-
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it could be happening
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it could have happened
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it could have been happening
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Negation 	
Einfache Form 	Form mit V-ing 	Perfekt 	Perfekt mit V-ing 	
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it couldn't happen
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it couldn't be happening
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it couldn't have happened
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it couldn't have been happening
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Fragende Form 	
Einfache Form 	Form mit V-ing 	Perfekt 	Perfekt mit V-ing 	
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could it happen?
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could it be happening?
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could it have happened?
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could it have been happening?
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Fragende Negation Form 	
Einfache Form 	Form mit V-ing 	Perfekt 	Perfekt mit V-ing 	
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couldn't it happen?
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couldn't it be happening?
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couldn't it have happened?
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couldn't it have been happening?
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