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