I could skip you could skip he could skip we could skip you could skip they could skip
V-ing form
I could be skipping you could be skipping he could be skipping we could be skipping you could be skipping they could be skipping
Perfect
I could have skipped you could have skipped he could have skipped we could have skipped you could have skipped they could have skipped
V-ing perfect
I could have been skipping you could have been skipping he could have been skipping we could have been skipping you could have been skipping they could have been skipping
Negation
Simple form
I could not skip you could not skip he could not skip we could not skip you could not skip they could not skip
V-ing form
I could not be skipping you could not be skipping he could not be skipping we could not be skipping you could not be skipping they could not be skipping
Perfect
I could not have skipped you could not have skipped he could not have skipped we could not have skipped you could not have skipped they could not have skipped
V-ing perfect
I could not have been skipping you could not have been skipping he could not have been skipping we could not have been skipping you could not have been skipping they could not have been skipping
Interrogative form
Simple form
could I skip? could you skip? could he skip? could we skip? could you skip? could they skip?
V-ing form
could I be skipping? could you be skipping? could he be skipping? could we be skipping? could you be skipping? could they be skipping?
Perfect
could I have skipped? could you have skipped? could he have skipped? could we have skipped? could you have skipped? could they have skipped?
V-ing perfect
could I have been skipping? could you have been skipping? could he have been skipping? could we have been skipping? could you have been skipping? could they have been skipping?
Interro-negative form
Simple form
could I not skip? could you not skip? could he not skip? could we not skip? could you not skip? could they not skip?
V-ing form
could I not be skipping? could you not be skipping? could he not be skipping? could we not be skipping? could you not be skipping? could they not be skipping?
Perfect
could I not have skipped? could you not have skipped? could he not have skipped? could we not have skipped? could you not have skipped? could they not have skipped?
V-ing perfect
could I not have been skipping? could you not have been skipping? could he not have been skipping? could we not have been skipping? could you not have been skipping? could they not have been skipping?