can quack
Regular verb: quack - quacked- quacked

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

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I cannot quack
you cannot quack
he cannot quack
we cannot quack
you cannot quack
they cannot quack 	I cannot be quacking
you cannot be quacking
he cannot be quacking
we cannot be quacking
you cannot be quacking
they cannot be quacking	I cannot have quacked
you cannot have quacked
he cannot have quacked
we cannot have quacked
you cannot have quacked
they cannot have quacked	I cannot have been quacking
you cannot have been quacking
he cannot have been quacking
we cannot have been quacking
you cannot have been quacking
they cannot have been quacking	

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

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