I can fall you can fall she can fall we can fall you can fall they can fall
V-ing form
I can be falling you can be falling she can be falling we can be falling you can be falling they can be falling
Perfect
I can have fallen you can have fallen she 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 she can have been falling we can have been falling you can have been falling they can have been falling
Negation
Simple form
I cannot fall you cannot fall she cannot fall we cannot fall you cannot fall they cannot fall
V-ing form
I cannot be falling you cannot be falling she cannot be falling we cannot be falling you cannot be falling they cannot be falling
Perfect
I cannot have fallen you cannot have fallen she cannot have fallen we cannot have fallen you cannot have fallen they cannot have fallen
V-ing perfect
I cannot have been falling you cannot have been falling she cannot have been falling we cannot have been falling you cannot have been falling they cannot have been falling
Interrogative form
Simple form
can I fall? can you fall? can she fall? can we fall? can you fall? can they fall?
V-ing form
can I be falling? can you be falling? can she be falling? can we be falling? can you be falling? can they be falling?
Perfect
can I have fallen? can you have fallen? can she 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 she have been falling? can we have been falling? can you have been falling? can they have been falling?
Interro-negative form
Simple form
can I not fall? can you not fall? can she not fall? can we not fall? can you not fall? can they not fall?
V-ing form
can I not be falling? can you not be falling? can she not be falling? can we not be falling? can you not be falling? can they not be falling?
Perfect
can I not have fallen? can you not have fallen? can she not have fallen? can we not have fallen? can you not have fallen? can they not have fallen?
V-ing perfect
can I not have been falling? can you not have been falling? can she not have been falling? can we not have been falling? can you not have been falling? can they not have been falling?