could lack
Regular verb: lack - lacked- lacked

Affirmation 	
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I could lack
you could lack
he could lack
we could lack
you could lack
they could lack 	I could be lacking
you could be lacking
he could be lacking
we could be lacking
you could be lacking
they could be lacking	I could have lacked
you could have lacked
he could have lacked
we could have lacked
you could have lacked
they could have lacked	I could have been lacking
you could have been lacking
he could have been lacking
we could have been lacking
you could have been lacking
they could have been lacking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not lack
you could not lack
he could not lack
we could not lack
you could not lack
they could not lack 	I could not be lacking
you could not be lacking
he could not be lacking
we could not be lacking
you could not be lacking
they could not be lacking	I could not have lacked
you could not have lacked
he could not have lacked
we could not have lacked
you could not have lacked
they could not have lacked	I could not have been lacking
you could not have been lacking
he could not have been lacking
we could not have been lacking
you could not have been lacking
they could not have been lacking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I lack?
could you lack?
could he lack?
could we lack?
could you lack?
could they lack? 	could I be lacking?
could you be lacking?
could he be lacking?
could we be lacking?
could you be lacking?
could they be lacking? 	could I have lacked?
could you have lacked?
could he have lacked?
could we have lacked?
could you have lacked?
could they have lacked? 	could I have been lacking?
could you have been lacking?
could he have been lacking?
could we have been lacking?
could you have been lacking?
could they have been lacking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not lack?
could you not lack?
could he not lack?
could we not lack?
could you not lack?
could they not lack? 	could I not be lacking?
could you not be lacking?
could he not be lacking?
could we not be lacking?
could you not be lacking?
could they not be lacking? 	could I not have lacked?
could you not have lacked?
could he not have lacked?
could we not have lacked?
could you not have lacked?
could they not have lacked? 	could I not have been lacking?
could you not have been lacking?
could he not have been lacking?
could we not have been lacking?
could you not have been lacking?
could they not have been lacking?