could rain
Regular verb: rain - rained- rained

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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it could rain
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it could be raining
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it could have rained
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it could have been raining
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Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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it could not rain
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it could not be raining
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it could not have rained
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it could not have been raining
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Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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could it rain?
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could it be raining?
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could it have rained?
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could it have been raining?
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Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
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could it not rain?
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could it not be raining?
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could it not have rained?
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could it not have been raining?
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