could grass
Regular verb: grass - grassed- grassed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could grass
you could grass
he could grass
we could grass
you could grass
they could grass 	I could be grassing
you could be grassing
he could be grassing
we could be grassing
you could be grassing
they could be grassing	I could have grassed
you could have grassed
he could have grassed
we could have grassed
you could have grassed
they could have grassed	I could have been grassing
you could have been grassing
he could have been grassing
we could have been grassing
you could have been grassing
they could have been grassing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I couldn't grass
you couldn't grass
he couldn't grass
we couldn't grass
you couldn't grass
they couldn't grass 	I couldn't be grassing
you couldn't be grassing
he couldn't be grassing
we couldn't be grassing
you couldn't be grassing
they couldn't be grassing	I couldn't have grassed
you couldn't have grassed
he couldn't have grassed
we couldn't have grassed
you couldn't have grassed
they couldn't have grassed	I couldn't have been grassing
you couldn't have been grassing
he couldn't have been grassing
we couldn't have been grassing
you couldn't have been grassing
they couldn't have been grassing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I grass?
could you grass?
could he grass?
could we grass?
could you grass?
could they grass? 	could I be grassing?
could you be grassing?
could he be grassing?
could we be grassing?
could you be grassing?
could they be grassing? 	could I have grassed?
could you have grassed?
could he have grassed?
could we have grassed?
could you have grassed?
could they have grassed? 	could I have been grassing?
could you have been grassing?
could he have been grassing?
could we have been grassing?
could you have been grassing?
could they have been grassing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
couldn't I grass?
couldn't you grass?
couldn't he grass?
couldn't we grass?
couldn't you grass?
couldn't they grass? 	couldn't I be grassing?
couldn't you be grassing?
couldn't he be grassing?
couldn't we be grassing?
couldn't you be grassing?
couldn't they be grassing? 	couldn't I have grassed?
couldn't you have grassed?
couldn't he have grassed?
couldn't we have grassed?
couldn't you have grassed?
couldn't they have grassed? 	couldn't I have been grassing?
couldn't you have been grassing?
couldn't he have been grassing?
couldn't we have been grassing?
couldn't you have been grassing?
couldn't they have been grassing?