English verb conjugation
CAN GRUB

Regular verb: grub - grubbed - grubbed

Affirmation

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

Negation

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

Interrogative form

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

Interro-negative form

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