I can sigh you can sigh he can sigh we can sigh you can sigh they can sigh
V-ing form
I can be sighing you can be sighing he can be sighing we can be sighing you can be sighing they can be sighing
Perfect
I can have sighed you can have sighed he can have sighed we can have sighed you can have sighed they can have sighed
V-ing perfect
I can have been sighing you can have been sighing he can have been sighing we can have been sighing you can have been sighing they can have been sighing
Negation
Simple form
I cannot sigh you cannot sigh he cannot sigh we cannot sigh you cannot sigh they cannot sigh
V-ing form
I cannot be sighing you cannot be sighing he cannot be sighing we cannot be sighing you cannot be sighing they cannot be sighing
Perfect
I cannot have sighed you cannot have sighed he cannot have sighed we cannot have sighed you cannot have sighed they cannot have sighed
V-ing perfect
I cannot have been sighing you cannot have been sighing he cannot have been sighing we cannot have been sighing you cannot have been sighing they cannot have been sighing
Interrogative form
Simple form
can I sigh? can you sigh? can he sigh? can we sigh? can you sigh? can they sigh?
V-ing form
can I be sighing? can you be sighing? can he be sighing? can we be sighing? can you be sighing? can they be sighing?
Perfect
can I have sighed? can you have sighed? can he have sighed? can we have sighed? can you have sighed? can they have sighed?
V-ing perfect
can I have been sighing? can you have been sighing? can he have been sighing? can we have been sighing? can you have been sighing? can they have been sighing?
Interro-negative form
Simple form
can I not sigh? can you not sigh? can he not sigh? can we not sigh? can you not sigh? can they not sigh?
V-ing form
can I not be sighing? can you not be sighing? can he not be sighing? can we not be sighing? can you not be sighing? can they not be sighing?
Perfect
can I not have sighed? can you not have sighed? can he not have sighed? can we not have sighed? can you not have sighed? can they not have sighed?
V-ing perfect
can I not have been sighing? can you not have been sighing? can he not have been sighing? can we not have been sighing? can you not have been sighing? can they not have been sighing?