could trill
Regular verb: trill - trilled- trilled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could trill
you could trill
she could trill
we could trill
you could trill
they could trill 	I could be trilling
you could be trilling
she could be trilling
we could be trilling
you could be trilling
they could be trilling	I could have trilled
you could have trilled
she could have trilled
we could have trilled
you could have trilled
they could have trilled	I could have been trilling
you could have been trilling
she could have been trilling
we could have been trilling
you could have been trilling
they could have been trilling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't trill
you couldn't trill
she couldn't trill
we couldn't trill
you couldn't trill
they couldn't trill 	I couldn't be trilling
you couldn't be trilling
she couldn't be trilling
we couldn't be trilling
you couldn't be trilling
they couldn't be trilling	I couldn't have trilled
you couldn't have trilled
she couldn't have trilled
we couldn't have trilled
you couldn't have trilled
they couldn't have trilled	I couldn't have been trilling
you couldn't have been trilling
she couldn't have been trilling
we couldn't have been trilling
you couldn't have been trilling
they couldn't have been trilling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I trill?
could you trill?
could she trill?
could we trill?
could you trill?
could they trill? 	could I be trilling?
could you be trilling?
could she be trilling?
could we be trilling?
could you be trilling?
could they be trilling? 	could I have trilled?
could you have trilled?
could she have trilled?
could we have trilled?
could you have trilled?
could they have trilled? 	could I have been trilling?
could you have been trilling?
could she have been trilling?
could we have been trilling?
could you have been trilling?
could they have been trilling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I trill?
couldn't you trill?
couldn't she trill?
couldn't we trill?
couldn't you trill?
couldn't they trill? 	couldn't I be trilling?
couldn't you be trilling?
couldn't she be trilling?
couldn't we be trilling?
couldn't you be trilling?
couldn't they be trilling? 	couldn't I have trilled?
couldn't you have trilled?
couldn't she have trilled?
couldn't we have trilled?
couldn't you have trilled?
couldn't they have trilled? 	couldn't I have been trilling?
couldn't you have been trilling?
couldn't she have been trilling?
couldn't we have been trilling?
couldn't you have been trilling?
couldn't they have been trilling?