could grub
Regular verb: grub - grubbed- grubbed

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could grub
you could grub
he could grub
we could grub
you could grub
they could grub 	I could be grubbing
you could be grubbing
he could be grubbing
we could be grubbing
you could be grubbing
they could be grubbing	I could have grubbed
you could have grubbed
he could have grubbed
we could have grubbed
you could have grubbed
they could have grubbed	I could have been grubbing
you could have been grubbing
he could have been grubbing
we could have been grubbing
you could have been grubbing
they could have been grubbing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I could not grub
you could not grub
he could not grub
we could not grub
you could not grub
they could not grub 	I could not be grubbing
you could not be grubbing
he could not be grubbing
we could not be grubbing
you could not be grubbing
they could not be grubbing	I could not have grubbed
you could not have grubbed
he could not have grubbed
we could not have grubbed
you could not have grubbed
they could not have grubbed	I could not have been grubbing
you could not have been grubbing
he could not have been grubbing
we could not have been grubbing
you could not have been grubbing
they could not have been grubbing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I grub?
could you grub?
could he grub?
could we grub?
could you grub?
could they grub? 	could I be grubbing?
could you be grubbing?
could he be grubbing?
could we be grubbing?
could you be grubbing?
could they be grubbing? 	could I have grubbed?
could you have grubbed?
could he have grubbed?
could we have grubbed?
could you have grubbed?
could they have grubbed? 	could I have been grubbing?
could you have been grubbing?
could he have been grubbing?
could we have been grubbing?
could you have been grubbing?
could they have been grubbing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
could I not grub?
could you not grub?
could he not grub?
could we not grub?
could you not grub?
could they not grub? 	could I not be grubbing?
could you not be grubbing?
could he not be grubbing?
could we not be grubbing?
could you not be grubbing?
could they not be grubbing? 	could I not have grubbed?
could you not have grubbed?
could he not have grubbed?
could we not have grubbed?
could you not have grubbed?
could they not have grubbed? 	could I not have been grubbing?
could you not have been grubbing?
could he not have been grubbing?
could we not have been grubbing?
could you not have been grubbing?
could they not have been grubbing?