could quack
Regular verb: quack - quacked- quacked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could quack
you could quack
she could quack
we could quack
you could quack
they could quack 	I could be quacking
you could be quacking
she could be quacking
we could be quacking
you could be quacking
they could be quacking	I could have quacked
you could have quacked
she could have quacked
we could have quacked
you could have quacked
they could have quacked	I could have been quacking
you could have been quacking
she could have been quacking
we could have been quacking
you could have been quacking
they could have been quacking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not quack
you could not quack
she could not quack
we could not quack
you could not quack
they could not quack 	I could not be quacking
you could not be quacking
she could not be quacking
we could not be quacking
you could not be quacking
they could not be quacking	I could not have quacked
you could not have quacked
she could not have quacked
we could not have quacked
you could not have quacked
they could not have quacked	I could not have been quacking
you could not have been quacking
she could not have been quacking
we could not have been quacking
you could not have been quacking
they could not have been quacking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I quack?
could you quack?
could she quack?
could we quack?
could you quack?
could they quack? 	could I be quacking?
could you be quacking?
could she be quacking?
could we be quacking?
could you be quacking?
could they be quacking? 	could I have quacked?
could you have quacked?
could she have quacked?
could we have quacked?
could you have quacked?
could they have quacked? 	could I have been quacking?
could you have been quacking?
could she have been quacking?
could we have been quacking?
could you have been quacking?
could they have been quacking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not quack?
could you not quack?
could she not quack?
could we not quack?
could you not quack?
could they not quack? 	could I not be quacking?
could you not be quacking?
could she not be quacking?
could we not be quacking?
could you not be quacking?
could they not be quacking? 	could I not have quacked?
could you not have quacked?
could she not have quacked?
could we not have quacked?
could you not have quacked?
could they not have quacked? 	could I not have been quacking?
could you not have been quacking?
could she not have been quacking?
could we not have been quacking?
could you not have been quacking?
could they not have been quacking?