I could speculate you could speculate he could speculate we could speculate you could speculate they could speculate
V-ing form
I could be speculating you could be speculating he could be speculating we could be speculating you could be speculating they could be speculating
Perfect
I could have speculated you could have speculated he could have speculated we could have speculated you could have speculated they could have speculated
V-ing perfect
I could have been speculating you could have been speculating he could have been speculating we could have been speculating you could have been speculating they could have been speculating
Negation
Simple form
I could not speculate you could not speculate he could not speculate we could not speculate you could not speculate they could not speculate
V-ing form
I could not be speculating you could not be speculating he could not be speculating we could not be speculating you could not be speculating they could not be speculating
Perfect
I could not have speculated you could not have speculated he could not have speculated we could not have speculated you could not have speculated they could not have speculated
V-ing perfect
I could not have been speculating you could not have been speculating he could not have been speculating we could not have been speculating you could not have been speculating they could not have been speculating
Interrogative form
Simple form
could I speculate? could you speculate? could he speculate? could we speculate? could you speculate? could they speculate?
V-ing form
could I be speculating? could you be speculating? could he be speculating? could we be speculating? could you be speculating? could they be speculating?
Perfect
could I have speculated? could you have speculated? could he have speculated? could we have speculated? could you have speculated? could they have speculated?
V-ing perfect
could I have been speculating? could you have been speculating? could he have been speculating? could we have been speculating? could you have been speculating? could they have been speculating?
Interro-negative form
Simple form
could I not speculate? could you not speculate? could he not speculate? could we not speculate? could you not speculate? could they not speculate?
V-ing form
could I not be speculating? could you not be speculating? could he not be speculating? could we not be speculating? could you not be speculating? could they not be speculating?
Perfect
could I not have speculated? could you not have speculated? could he not have speculated? could we not have speculated? could you not have speculated? could they not have speculated?
V-ing perfect
could I not have been speculating? could you not have been speculating? could he not have been speculating? could we not have been speculating? could you not have been speculating? could they not have been speculating?