could tusk
Regular verb: tusk - tusked- tusked

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could tusk
you could tusk
he could tusk
we could tusk
you could tusk
they could tusk 	I could be tusking
you could be tusking
he could be tusking
we could be tusking
you could be tusking
they could be tusking	I could have tusked
you could have tusked
he could have tusked
we could have tusked
you could have tusked
they could have tusked	I could have been tusking
you could have been tusking
he could have been tusking
we could have been tusking
you could have been tusking
they could have been tusking	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not tusk
you could not tusk
he could not tusk
we could not tusk
you could not tusk
they could not tusk 	I could not be tusking
you could not be tusking
he could not be tusking
we could not be tusking
you could not be tusking
they could not be tusking	I could not have tusked
you could not have tusked
he could not have tusked
we could not have tusked
you could not have tusked
they could not have tusked	I could not have been tusking
you could not have been tusking
he could not have been tusking
we could not have been tusking
you could not have been tusking
they could not have been tusking	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I tusk?
could you tusk?
could he tusk?
could we tusk?
could you tusk?
could they tusk? 	could I be tusking?
could you be tusking?
could he be tusking?
could we be tusking?
could you be tusking?
could they be tusking? 	could I have tusked?
could you have tusked?
could he have tusked?
could we have tusked?
could you have tusked?
could they have tusked? 	could I have been tusking?
could you have been tusking?
could he have been tusking?
could we have been tusking?
could you have been tusking?
could they have been tusking? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not tusk?
could you not tusk?
could he not tusk?
could we not tusk?
could you not tusk?
could they not tusk? 	could I not be tusking?
could you not be tusking?
could he not be tusking?
could we not be tusking?
could you not be tusking?
could they not be tusking? 	could I not have tusked?
could you not have tusked?
could he not have tusked?
could we not have tusked?
could you not have tusked?
could they not have tusked? 	could I not have been tusking?
could you not have been tusking?
could he not have been tusking?
could we not have been tusking?
could you not have been tusking?
could they not have been tusking?