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