I could conceal you could conceal he could conceal we could conceal you could conceal they could conceal
V-ing form
I could be concealing you could be concealing he could be concealing we could be concealing you could be concealing they could be concealing
Perfect
I could have concealed you could have concealed he could have concealed we could have concealed you could have concealed they could have concealed
V-ing perfect
I could have been concealing you could have been concealing he could have been concealing we could have been concealing you could have been concealing they could have been concealing
Negation
Simple form
I could not conceal you could not conceal he could not conceal we could not conceal you could not conceal they could not conceal
V-ing form
I could not be concealing you could not be concealing he could not be concealing we could not be concealing you could not be concealing they could not be concealing
Perfect
I could not have concealed you could not have concealed he could not have concealed we could not have concealed you could not have concealed they could not have concealed
V-ing perfect
I could not have been concealing you could not have been concealing he could not have been concealing we could not have been concealing you could not have been concealing they could not have been concealing
Interrogative form
Simple form
could I conceal? could you conceal? could he conceal? could we conceal? could you conceal? could they conceal?
V-ing form
could I be concealing? could you be concealing? could he be concealing? could we be concealing? could you be concealing? could they be concealing?
Perfect
could I have concealed? could you have concealed? could he have concealed? could we have concealed? could you have concealed? could they have concealed?
V-ing perfect
could I have been concealing? could you have been concealing? could he have been concealing? could we have been concealing? could you have been concealing? could they have been concealing?
Interro-negative form
Simple form
could I not conceal? could you not conceal? could he not conceal? could we not conceal? could you not conceal? could they not conceal?
V-ing form
could I not be concealing? could you not be concealing? could he not be concealing? could we not be concealing? could you not be concealing? could they not be concealing?
Perfect
could I not have concealed? could you not have concealed? could he not have concealed? could we not have concealed? could you not have concealed? could they not have concealed?
V-ing perfect
could I not have been concealing? could you not have been concealing? could he not have been concealing? could we not have been concealing? could you not have been concealing? could they not have been concealing?