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