could yell
Regular verb: yell - yelled- yelled

Affirmation 	
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I could yell
you could yell
she could yell
we could yell
you could yell
they could yell 	I could be yelling
you could be yelling
she could be yelling
we could be yelling
you could be yelling
they could be yelling	I could have yelled
you could have yelled
she could have yelled
we could have yelled
you could have yelled
they could have yelled	I could have been yelling
you could have been yelling
she could have been yelling
we could have been yelling
you could have been yelling
they could have been yelling	

Negation 	
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I couldn't yell
you couldn't yell
she couldn't yell
we couldn't yell
you couldn't yell
they couldn't yell 	I couldn't be yelling
you couldn't be yelling
she couldn't be yelling
we couldn't be yelling
you couldn't be yelling
they couldn't be yelling	I couldn't have yelled
you couldn't have yelled
she couldn't have yelled
we couldn't have yelled
you couldn't have yelled
they couldn't have yelled	I couldn't have been yelling
you couldn't have been yelling
she couldn't have been yelling
we couldn't have been yelling
you couldn't have been yelling
they couldn't have been yelling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I yell?
could you yell?
could she yell?
could we yell?
could you yell?
could they yell? 	could I be yelling?
could you be yelling?
could she be yelling?
could we be yelling?
could you be yelling?
could they be yelling? 	could I have yelled?
could you have yelled?
could she have yelled?
could we have yelled?
could you have yelled?
could they have yelled? 	could I have been yelling?
could you have been yelling?
could she have been yelling?
could we have been yelling?
could you have been yelling?
could they have been yelling? 	

Interro-negative form 	
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couldn't I yell?
couldn't you yell?
couldn't she yell?
couldn't we yell?
couldn't you yell?
couldn't they yell? 	couldn't I be yelling?
couldn't you be yelling?
couldn't she be yelling?
couldn't we be yelling?
couldn't you be yelling?
couldn't they be yelling? 	couldn't I have yelled?
couldn't you have yelled?
couldn't she have yelled?
couldn't we have yelled?
couldn't you have yelled?
couldn't they have yelled? 	couldn't I have been yelling?
couldn't you have been yelling?
couldn't she have been yelling?
couldn't we have been yelling?
couldn't you have been yelling?
couldn't they have been yelling?