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 cannot untie you cannot untie he cannot untie we cannot untie you cannot untie they cannot untie
V-ing form
I cannot be untying you cannot be untying he cannot be untying we cannot be untying you cannot be untying they cannot be untying
Perfect
I cannot have untied you cannot have untied he cannot have untied we cannot have untied you cannot have untied they cannot have untied
V-ing perfect
I cannot have been untying you cannot have been untying he cannot have been untying we cannot have been untying you cannot have been untying they cannot 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 I not untie? can you not untie? can he not untie? can we not untie? can you not untie? can they not untie?
V-ing form
can I not be untying? can you not be untying? can he not be untying? can we not be untying? can you not be untying? can they not be untying?
Perfect
can I not have untied? can you not have untied? can he not have untied? can we not have untied? can you not have untied? can they not have untied?
V-ing perfect
can I not have been untying? can you not have been untying? can he not have been untying? can we not have been untying? can you not have been untying? can they not have been untying?