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