I could trip you could trip he could trip we could trip you could trip they could trip
V-ing form
I could be tripping you could be tripping he could be tripping we could be tripping you could be tripping they could be tripping
Perfect
I could have tripped you could have tripped he could have tripped we could have tripped you could have tripped they could have tripped
V-ing perfect
I could have been tripping you could have been tripping he could have been tripping we could have been tripping you could have been tripping they could have been tripping
Negation
Simple form
I could not trip you could not trip he could not trip we could not trip you could not trip they could not trip
V-ing form
I could not be tripping you could not be tripping he could not be tripping we could not be tripping you could not be tripping they could not be tripping
Perfect
I could not have tripped you could not have tripped he could not have tripped we could not have tripped you could not have tripped they could not have tripped
V-ing perfect
I could not have been tripping you could not have been tripping he could not have been tripping we could not have been tripping you could not have been tripping they could not have been tripping
Interrogative form
Simple form
could I trip? could you trip? could he trip? could we trip? could you trip? could they trip?
V-ing form
could I be tripping? could you be tripping? could he be tripping? could we be tripping? could you be tripping? could they be tripping?
Perfect
could I have tripped? could you have tripped? could he have tripped? could we have tripped? could you have tripped? could they have tripped?
V-ing perfect
could I have been tripping? could you have been tripping? could he have been tripping? could we have been tripping? could you have been tripping? could they have been tripping?
Interro-negative form
Simple form
could I not trip? could you not trip? could he not trip? could we not trip? could you not trip? could they not trip?
V-ing form
could I not be tripping? could you not be tripping? could he not be tripping? could we not be tripping? could you not be tripping? could they not be tripping?
Perfect
could I not have tripped? could you not have tripped? could he not have tripped? could we not have tripped? could you not have tripped? could they not have tripped?
V-ing perfect
could I not have been tripping? could you not have been tripping? could he not have been tripping? could we not have been tripping? could you not have been tripping? could they not have been tripping?