English verb conjugation
COULD DRUB

Regular verb: drub - drubbed - drubbed

Affirmation

Simple form	V-ing form
I could drub you could drub he could drub we could drub you could drub they could drub	I could be drubbing you could be drubbing he could be drubbing we could be drubbing you could be drubbing they could be drubbing
Perfect	V-ing perfect
I could have drubbed you could have drubbed he could have drubbed we could have drubbed you could have drubbed they could have drubbed	I could have been drubbing you could have been drubbing he could have been drubbing we could have been drubbing you could have been drubbing they could have been drubbing

Negation

Simple form	V-ing form
I couldn't drub you couldn't drub he couldn't drub we couldn't drub you couldn't drub they couldn't drub	I couldn't be drubbing you couldn't be drubbing he couldn't be drubbing we couldn't be drubbing you couldn't be drubbing they couldn't be drubbing
Perfect	V-ing perfect
I couldn't have drubbed you couldn't have drubbed he couldn't have drubbed we couldn't have drubbed you couldn't have drubbed they couldn't have drubbed	I couldn't have been drubbing you couldn't have been drubbing he couldn't have been drubbing we couldn't have been drubbing you couldn't have been drubbing they couldn't have been drubbing

Interrogative form

Simple form	V-ing form
could I drub? could you drub? could he drub? could we drub? could you drub? could they drub?	could I be drubbing? could you be drubbing? could he be drubbing? could we be drubbing? could you be drubbing? could they be drubbing?
Perfect	V-ing perfect
could I have drubbed? could you have drubbed? could he have drubbed? could we have drubbed? could you have drubbed? could they have drubbed?	could I have been drubbing? could you have been drubbing? could he have been drubbing? could we have been drubbing? could you have been drubbing? could they have been drubbing?

Interro-negative form

Simple form	V-ing form
couldn't I drub? couldn't you drub? couldn't he drub? couldn't we drub? couldn't you drub? couldn't they drub?	couldn't I be drubbing? couldn't you be drubbing? couldn't he be drubbing? couldn't we be drubbing? couldn't you be drubbing? couldn't they be drubbing?
Perfect	V-ing perfect
couldn't I have drubbed? couldn't you have drubbed? couldn't he have drubbed? couldn't we have drubbed? couldn't you have drubbed? couldn't they have drubbed?	couldn't I have been drubbing? couldn't you have been drubbing? couldn't he have been drubbing? couldn't we have been drubbing? couldn't you have been drubbing? couldn't they have been drubbing?