could chalk
Regular verb: chalk - chalked- chalked

Affirmation 	
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I could chalk
you could chalk
she could chalk
we could chalk
you could chalk
they could chalk 	I could be chalking
you could be chalking
she could be chalking
we could be chalking
you could be chalking
they could be chalking	I could have chalked
you could have chalked
she could have chalked
we could have chalked
you could have chalked
they could have chalked	I could have been chalking
you could have been chalking
she could have been chalking
we could have been chalking
you could have been chalking
they could have been chalking	

Negation 	
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I could not chalk
you could not chalk
she could not chalk
we could not chalk
you could not chalk
they could not chalk 	I could not be chalking
you could not be chalking
she could not be chalking
we could not be chalking
you could not be chalking
they could not be chalking	I could not have chalked
you could not have chalked
she could not have chalked
we could not have chalked
you could not have chalked
they could not have chalked	I could not have been chalking
you could not have been chalking
she could not have been chalking
we could not have been chalking
you could not have been chalking
they could not have been chalking	

Interrogative form 	
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could I chalk?
could you chalk?
could she chalk?
could we chalk?
could you chalk?
could they chalk? 	could I be chalking?
could you be chalking?
could she be chalking?
could we be chalking?
could you be chalking?
could they be chalking? 	could I have chalked?
could you have chalked?
could she have chalked?
could we have chalked?
could you have chalked?
could they have chalked? 	could I have been chalking?
could you have been chalking?
could she have been chalking?
could we have been chalking?
could you have been chalking?
could they have been chalking? 	

Interro-negative form 	
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could I not chalk?
could you not chalk?
could she not chalk?
could we not chalk?
could you not chalk?
could they not chalk? 	could I not be chalking?
could you not be chalking?
could she not be chalking?
could we not be chalking?
could you not be chalking?
could they not be chalking? 	could I not have chalked?
could you not have chalked?
could she not have chalked?
could we not have chalked?
could you not have chalked?
could they not have chalked? 	could I not have been chalking?
could you not have been chalking?
could she not have been chalking?
could we not have been chalking?
could you not have been chalking?
could they not have been chalking?