could whistle
Regular verb: whistle - whistled- whistled

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could whistle
you could whistle
she could whistle
we could whistle
you could whistle
they could whistle 	I could be whistling
you could be whistling
she could be whistling
we could be whistling
you could be whistling
they could be whistling	I could have whistled
you could have whistled
she could have whistled
we could have whistled
you could have whistled
they could have whistled	I could have been whistling
you could have been whistling
she could have been whistling
we could have been whistling
you could have been whistling
they could have been whistling	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't whistle
you couldn't whistle
she couldn't whistle
we couldn't whistle
you couldn't whistle
they couldn't whistle 	I couldn't be whistling
you couldn't be whistling
she couldn't be whistling
we couldn't be whistling
you couldn't be whistling
they couldn't be whistling	I couldn't have whistled
you couldn't have whistled
she couldn't have whistled
we couldn't have whistled
you couldn't have whistled
they couldn't have whistled	I couldn't have been whistling
you couldn't have been whistling
she couldn't have been whistling
we couldn't have been whistling
you couldn't have been whistling
they couldn't have been whistling	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I whistle?
could you whistle?
could she whistle?
could we whistle?
could you whistle?
could they whistle? 	could I be whistling?
could you be whistling?
could she be whistling?
could we be whistling?
could you be whistling?
could they be whistling? 	could I have whistled?
could you have whistled?
could she have whistled?
could we have whistled?
could you have whistled?
could they have whistled? 	could I have been whistling?
could you have been whistling?
could she have been whistling?
could we have been whistling?
could you have been whistling?
could they have been whistling? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I whistle?
couldn't you whistle?
couldn't she whistle?
couldn't we whistle?
couldn't you whistle?
couldn't they whistle? 	couldn't I be whistling?
couldn't you be whistling?
couldn't she be whistling?
couldn't we be whistling?
couldn't you be whistling?
couldn't they be whistling? 	couldn't I have whistled?
couldn't you have whistled?
couldn't she have whistled?
couldn't we have whistled?
couldn't you have whistled?
couldn't they have whistled? 	couldn't I have been whistling?
couldn't you have been whistling?
couldn't she have been whistling?
couldn't we have been whistling?
couldn't you have been whistling?
couldn't they have been whistling?