I can untie you can untie he can untie we can untie you can untie they can untie
V-ing form
I can be untying you can be untying he can be untying we can be untying you can be untying they can be untying
Perfect
I can have untied you can have untied he can have untied we can have untied you can have untied they can have untied
V-ing perfect
I can have been untying you can have been untying he can have been untying we can have been untying you can have been untying they can have been untying
Negation
Simple form
I can't untie you can't untie he can't untie we can't untie you can't untie they can't untie
V-ing form
I can't be untying you can't be untying he can't be untying we can't be untying you can't be untying they can't be untying
Perfect
I can't have untied you can't have untied he can't have untied we can't have untied you can't have untied they can't have untied
V-ing perfect
I can't have been untying you can't have been untying he can't have been untying we can't have been untying you can't have been untying they can't have been untying
Interrogative form
Simple form
can I untie? can you untie? can he untie? can we untie? can you untie? can they untie?
V-ing form
can I be untying? can you be untying? can he be untying? can we be untying? can you be untying? can they be untying?
Perfect
can I have untied? can you have untied? can he have untied? can we have untied? can you have untied? can they have untied?
V-ing perfect
can I have been untying? can you have been untying? can he have been untying? can we have been untying? can you have been untying? can they have been untying?
Interro-negative form
Simple form
can't I untie? can't you untie? can't he untie? can't we untie? can't you untie? can't they untie?
V-ing form
can't I be untying? can't you be untying? can't he be untying? can't we be untying? can't you be untying? can't they be untying?
Perfect
can't I have untied? can't you have untied? can't he have untied? can't we have untied? can't you have untied? can't they have untied?
V-ing perfect
can't I have been untying? can't you have been untying? can't he have been untying? can't we have been untying? can't you have been untying? can't they have been untying?