I can fall you can fall he can fall we can fall you can fall they can fall
V-ing form
I can be falling you can be falling he can be falling we can be falling you can be falling they can be falling
Perfect
I can have fallen you can have fallen he can have fallen we can have fallen you can have fallen they can have fallen
V-ing perfect
I can have been falling you can have been falling he can have been falling we can have been falling you can have been falling they can have been falling
Negation
Simple form
I can't fall you can't fall he can't fall we can't fall you can't fall they can't fall
V-ing form
I can't be falling you can't be falling he can't be falling we can't be falling you can't be falling they can't be falling
Perfect
I can't have fallen you can't have fallen he can't have fallen we can't have fallen you can't have fallen they can't have fallen
V-ing perfect
I can't have been falling you can't have been falling he can't have been falling we can't have been falling you can't have been falling they can't have been falling
Interrogative form
Simple form
can I fall? can you fall? can he fall? can we fall? can you fall? can they fall?
V-ing form
can I be falling? can you be falling? can he be falling? can we be falling? can you be falling? can they be falling?
Perfect
can I have fallen? can you have fallen? can he have fallen? can we have fallen? can you have fallen? can they have fallen?
V-ing perfect
can I have been falling? can you have been falling? can he have been falling? can we have been falling? can you have been falling? can they have been falling?
Interro-negative form
Simple form
can't I fall? can't you fall? can't he fall? can't we fall? can't you fall? can't they fall?
V-ing form
can't I be falling? can't you be falling? can't he be falling? can't we be falling? can't you be falling? can't they be falling?
Perfect
can't I have fallen? can't you have fallen? can't he have fallen? can't we have fallen? can't you have fallen? can't they have fallen?
V-ing perfect
can't I have been falling? can't you have been falling? can't he have been falling? can't we have been falling? can't you have been falling? can't they have been falling?