English verb conjugation
COULD KNOCK

Regular verb: knock - knocked - knocked

Affirmation

Simple form	V-ing form
I could knock you could knock she could knock we could knock you could knock they could knock	I could be knocking you could be knocking she could be knocking we could be knocking you could be knocking they could be knocking
Perfect	V-ing perfect
I could have knocked you could have knocked she could have knocked we could have knocked you could have knocked they could have knocked	I could have been knocking you could have been knocking she could have been knocking we could have been knocking you could have been knocking they could have been knocking

Negation

Simple form	V-ing form
I could not knock you could not knock she could not knock we could not knock you could not knock they could not knock	I could not be knocking you could not be knocking she could not be knocking we could not be knocking you could not be knocking they could not be knocking
Perfect	V-ing perfect
I could not have knocked you could not have knocked she could not have knocked we could not have knocked you could not have knocked they could not have knocked	I could not have been knocking you could not have been knocking she could not have been knocking we could not have been knocking you could not have been knocking they could not have been knocking

Interrogative form

Simple form	V-ing form
could I knock? could you knock? could she knock? could we knock? could you knock? could they knock?	could I be knocking? could you be knocking? could she be knocking? could we be knocking? could you be knocking? could they be knocking?
Perfect	V-ing perfect
could I have knocked? could you have knocked? could she have knocked? could we have knocked? could you have knocked? could they have knocked?	could I have been knocking? could you have been knocking? could she have been knocking? could we have been knocking? could you have been knocking? could they have been knocking?

Interro-negative form

Simple form	V-ing form
could I not knock? could you not knock? could she not knock? could we not knock? could you not knock? could they not knock?	could I not be knocking? could you not be knocking? could she not be knocking? could we not be knocking? could you not be knocking? could they not be knocking?
Perfect	V-ing perfect
could I not have knocked? could you not have knocked? could she not have knocked? could we not have knocked? could you not have knocked? could they not have knocked?	could I not have been knocking? could you not have been knocking? could she not have been knocking? could we not have been knocking? could you not have been knocking? could they not have been knocking?