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