I can sigh you can sigh she can sigh we can sigh you can sigh they can sigh
V-ing form
I can be sighing you can be sighing she can be sighing we can be sighing you can be sighing they can be sighing
Perfect
I can have sighed you can have sighed she 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 she 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 she cannot sigh we cannot sigh you cannot sigh they cannot sigh
V-ing form
I cannot be sighing you cannot be sighing she cannot be sighing we cannot be sighing you cannot be sighing they cannot be sighing
Perfect
I cannot have sighed you cannot have sighed she 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 she 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 she sigh? can we sigh? can you sigh? can they sigh?
V-ing form
can I be sighing? can you be sighing? can she be sighing? can we be sighing? can you be sighing? can they be sighing?
Perfect
can I have sighed? can you have sighed? can she 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 she 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 she 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 she 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 she 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 she not have been sighing? can we not have been sighing? can you not have been sighing? can they not have been sighing?