I can fork you can fork he can fork we can fork you can fork they can fork
V-ing form
I can be forking you can be forking he can be forking we can be forking you can be forking they can be forking
Perfect
I can have forked you can have forked he can have forked we can have forked you can have forked they can have forked
V-ing perfect
I can have been forking you can have been forking he can have been forking we can have been forking you can have been forking they can have been forking
Negation
Simple form
I cannot fork you cannot fork he cannot fork we cannot fork you cannot fork they cannot fork
V-ing form
I cannot be forking you cannot be forking he cannot be forking we cannot be forking you cannot be forking they cannot be forking
Perfect
I cannot have forked you cannot have forked he cannot have forked we cannot have forked you cannot have forked they cannot have forked
V-ing perfect
I cannot have been forking you cannot have been forking he cannot have been forking we cannot have been forking you cannot have been forking they cannot have been forking
Interrogative form
Simple form
can I fork? can you fork? can he fork? can we fork? can you fork? can they fork?
V-ing form
can I be forking? can you be forking? can he be forking? can we be forking? can you be forking? can they be forking?
Perfect
can I have forked? can you have forked? can he have forked? can we have forked? can you have forked? can they have forked?
V-ing perfect
can I have been forking? can you have been forking? can he have been forking? can we have been forking? can you have been forking? can they have been forking?
Interro-negative form
Simple form
can I not fork? can you not fork? can he not fork? can we not fork? can you not fork? can they not fork?
V-ing form
can I not be forking? can you not be forking? can he not be forking? can we not be forking? can you not be forking? can they not be forking?
Perfect
can I not have forked? can you not have forked? can he not have forked? can we not have forked? can you not have forked? can they not have forked?
V-ing perfect
can I not have been forking? can you not have been forking? can he not have been forking? can we not have been forking? can you not have been forking? can they not have been forking?