I could drill you could drill she could drill we could drill you could drill they could drill
V-ing form
I could be drilling you could be drilling she could be drilling we could be drilling you could be drilling they could be drilling
Perfect
I could have drilled you could have drilled she could have drilled we could have drilled you could have drilled they could have drilled
V-ing perfect
I could have been drilling you could have been drilling she could have been drilling we could have been drilling you could have been drilling they could have been drilling
Negation
Simple form
I could not drill you could not drill she could not drill we could not drill you could not drill they could not drill
V-ing form
I could not be drilling you could not be drilling she could not be drilling we could not be drilling you could not be drilling they could not be drilling
Perfect
I could not have drilled you could not have drilled she could not have drilled we could not have drilled you could not have drilled they could not have drilled
V-ing perfect
I could not have been drilling you could not have been drilling she could not have been drilling we could not have been drilling you could not have been drilling they could not have been drilling
Interrogative form
Simple form
could I drill? could you drill? could she drill? could we drill? could you drill? could they drill?
V-ing form
could I be drilling? could you be drilling? could she be drilling? could we be drilling? could you be drilling? could they be drilling?
Perfect
could I have drilled? could you have drilled? could she have drilled? could we have drilled? could you have drilled? could they have drilled?
V-ing perfect
could I have been drilling? could you have been drilling? could she have been drilling? could we have been drilling? could you have been drilling? could they have been drilling?
Interro-negative form
Simple form
could I not drill? could you not drill? could she not drill? could we not drill? could you not drill? could they not drill?
V-ing form
could I not be drilling? could you not be drilling? could she not be drilling? could we not be drilling? could you not be drilling? could they not be drilling?
Perfect
could I not have drilled? could you not have drilled? could she not have drilled? could we not have drilled? could you not have drilled? could they not have drilled?
V-ing perfect
could I not have been drilling? could you not have been drilling? could she not have been drilling? could we not have been drilling? could you not have been drilling? could they not have been drilling?