I could border you could border he could border we could border you could border they could border
V-ing form
I could be bordering you could be bordering he could be bordering we could be bordering you could be bordering they could be bordering
Perfect
I could have bordered you could have bordered he could have bordered we could have bordered you could have bordered they could have bordered
V-ing perfect
I could have been bordering you could have been bordering he could have been bordering we could have been bordering you could have been bordering they could have been bordering
Negation
Simple form
I could not border you could not border he could not border we could not border you could not border they could not border
V-ing form
I could not be bordering you could not be bordering he could not be bordering we could not be bordering you could not be bordering they could not be bordering
Perfect
I could not have bordered you could not have bordered he could not have bordered we could not have bordered you could not have bordered they could not have bordered
V-ing perfect
I could not have been bordering you could not have been bordering he could not have been bordering we could not have been bordering you could not have been bordering they could not have been bordering
Interrogative form
Simple form
could I border? could you border? could he border? could we border? could you border? could they border?
V-ing form
could I be bordering? could you be bordering? could he be bordering? could we be bordering? could you be bordering? could they be bordering?
Perfect
could I have bordered? could you have bordered? could he have bordered? could we have bordered? could you have bordered? could they have bordered?
V-ing perfect
could I have been bordering? could you have been bordering? could he have been bordering? could we have been bordering? could you have been bordering? could they have been bordering?
Interro-negative form
Simple form
could I not border? could you not border? could he not border? could we not border? could you not border? could they not border?
V-ing form
could I not be bordering? could you not be bordering? could he not be bordering? could we not be bordering? could you not be bordering? could they not be bordering?
Perfect
could I not have bordered? could you not have bordered? could he not have bordered? could we not have bordered? could you not have bordered? could they not have bordered?
V-ing perfect
could I not have been bordering? could you not have been bordering? could he not have been bordering? could we not have been bordering? could you not have been bordering? could they not have been bordering?