must snow
Regular verb: snow - snowed- snowed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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it must snow
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it must be snowing
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it must have snowed
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it must have been snowing
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Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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it mustn't snow
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it mustn't be snowing
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it mustn't have snowed
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it mustn't have been snowing
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Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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must it snow?
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must it be snowing?
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must it have snowed?
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must it have been snowing?
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Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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mustn't it snow?
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mustn't it be snowing?
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mustn't it have snowed?
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mustn't it have been snowing?
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