I could concertise you could concertise he could concertise we could concertise you could concertise they could concertise
V-ing form
I could be concertising you could be concertising he could be concertising we could be concertising you could be concertising they could be concertising
Perfect
I could have concertised you could have concertised he could have concertised we could have concertised you could have concertised they could have concertised
V-ing perfect
I could have been concertising you could have been concertising he could have been concertising we could have been concertising you could have been concertising they could have been concertising
Negation
Simple form
I couldn't concertise you couldn't concertise he couldn't concertise we couldn't concertise you couldn't concertise they couldn't concertise
V-ing form
I couldn't be concertising you couldn't be concertising he couldn't be concertising we couldn't be concertising you couldn't be concertising they couldn't be concertising
Perfect
I couldn't have concertised you couldn't have concertised he couldn't have concertised we couldn't have concertised you couldn't have concertised they couldn't have concertised
V-ing perfect
I couldn't have been concertising you couldn't have been concertising he couldn't have been concertising we couldn't have been concertising you couldn't have been concertising they couldn't have been concertising
Interrogative form
Simple form
could I concertise? could you concertise? could he concertise? could we concertise? could you concertise? could they concertise?
V-ing form
could I be concertising? could you be concertising? could he be concertising? could we be concertising? could you be concertising? could they be concertising?
Perfect
could I have concertised? could you have concertised? could he have concertised? could we have concertised? could you have concertised? could they have concertised?
V-ing perfect
could I have been concertising? could you have been concertising? could he have been concertising? could we have been concertising? could you have been concertising? could they have been concertising?
Interro-negative form
Simple form
couldn't I concertise? couldn't you concertise? couldn't he concertise? couldn't we concertise? couldn't you concertise? couldn't they concertise?
V-ing form
couldn't I be concertising? couldn't you be concertising? couldn't he be concertising? couldn't we be concertising? couldn't you be concertising? couldn't they be concertising?
Perfect
couldn't I have concertised? couldn't you have concertised? couldn't he have concertised? couldn't we have concertised? couldn't you have concertised? couldn't they have concertised?
V-ing perfect
couldn't I have been concertising? couldn't you have been concertising? couldn't he have been concertising? couldn't we have been concertising? couldn't you have been concertising? couldn't they have been concertising?