can clack
Regular verb: clack - clacked- clacked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I can clack
you can clack
she can clack
we can clack
you can clack
they can clack 	I can be clacking
you can be clacking
she can be clacking
we can be clacking
you can be clacking
they can be clacking	I can have clacked
you can have clacked
she can have clacked
we can have clacked
you can have clacked
they can have clacked	I can have been clacking
you can have been clacking
she can have been clacking
we can have been clacking
you can have been clacking
they can have been clacking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I cannot clack
you cannot clack
she cannot clack
we cannot clack
you cannot clack
they cannot clack 	I cannot be clacking
you cannot be clacking
she cannot be clacking
we cannot be clacking
you cannot be clacking
they cannot be clacking	I cannot have clacked
you cannot have clacked
she cannot have clacked
we cannot have clacked
you cannot have clacked
they cannot have clacked	I cannot have been clacking
you cannot have been clacking
she cannot have been clacking
we cannot have been clacking
you cannot have been clacking
they cannot have been clacking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I clack?
can you clack?
can she clack?
can we clack?
can you clack?
can they clack? 	can I be clacking?
can you be clacking?
can she be clacking?
can we be clacking?
can you be clacking?
can they be clacking? 	can I have clacked?
can you have clacked?
can she have clacked?
can we have clacked?
can you have clacked?
can they have clacked? 	can I have been clacking?
can you have been clacking?
can she have been clacking?
can we have been clacking?
can you have been clacking?
can they have been clacking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
can I not clack?
can you not clack?
can she not clack?
can we not clack?
can you not clack?
can they not clack? 	can I not be clacking?
can you not be clacking?
can she not be clacking?
can we not be clacking?
can you not be clacking?
can they not be clacking? 	can I not have clacked?
can you not have clacked?
can she not have clacked?
can we not have clacked?
can you not have clacked?
can they not have clacked? 	can I not have been clacking?
can you not have been clacking?
can she not have been clacking?
can we not have been clacking?
can you not have been clacking?
can they not have been clacking?