I can suffer you can suffer he can suffer we can suffer you can suffer they can suffer
V-ing form
I can be suffering you can be suffering he can be suffering we can be suffering you can be suffering they can be suffering
Perfect
I can have suffered you can have suffered he can have suffered we can have suffered you can have suffered they can have suffered
V-ing perfect
I can have been suffering you can have been suffering he can have been suffering we can have been suffering you can have been suffering they can have been suffering
Negation
Simple form
I can't suffer you can't suffer he can't suffer we can't suffer you can't suffer they can't suffer
V-ing form
I can't be suffering you can't be suffering he can't be suffering we can't be suffering you can't be suffering they can't be suffering
Perfect
I can't have suffered you can't have suffered he can't have suffered we can't have suffered you can't have suffered they can't have suffered
V-ing perfect
I can't have been suffering you can't have been suffering he can't have been suffering we can't have been suffering you can't have been suffering they can't have been suffering
Interrogative form
Simple form
can I suffer? can you suffer? can he suffer? can we suffer? can you suffer? can they suffer?
V-ing form
can I be suffering? can you be suffering? can he be suffering? can we be suffering? can you be suffering? can they be suffering?
Perfect
can I have suffered? can you have suffered? can he have suffered? can we have suffered? can you have suffered? can they have suffered?
V-ing perfect
can I have been suffering? can you have been suffering? can he have been suffering? can we have been suffering? can you have been suffering? can they have been suffering?
Interro-negative form
Simple form
can't I suffer? can't you suffer? can't he suffer? can't we suffer? can't you suffer? can't they suffer?
V-ing form
can't I be suffering? can't you be suffering? can't he be suffering? can't we be suffering? can't you be suffering? can't they be suffering?
Perfect
can't I have suffered? can't you have suffered? can't he have suffered? can't we have suffered? can't you have suffered? can't they have suffered?
V-ing perfect
can't I have been suffering? can't you have been suffering? can't he have been suffering? can't we have been suffering? can't you have been suffering? can't they have been suffering?